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libtdevnc/x11vnc/README

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x11vnc README file Date: Tue May 17 14:39:38 EDT 2005
The following information is taken from these URLs:
http://www.karlrunge.com/x11vnc/index.html
http://www.karlrunge.com/x11vnc/x11vnc_opts.html
they contain the most up to date info.
=======================================================================
http://www.karlrunge.com/x11vnc/index.html:
_________________________________________________________________
x11vnc: a VNC server for real X displays
(to [1]FAQ) (to [2]Downloads) (to [3]Building) (to
[4]Donations) (to [5]Beta Test)
x11vnc allows one to remotely view and interact with real X displays
(i.e. a display corresponding to a physical monitor, keyboard, and
mouse) with any VNC viewer. In this way it plays the role for Unix/X11
that WinVNC plays for Windows.
I wrote x11vnc because x0rfbserver was basically impossible to build
on Solaris and had poor performance. The primary x0rfbserver build
problems centered around esoteric C++ toolkits. x11vnc is written in
plain C and uses only standard libraries. I also added a few
enhancements to improve the interactive response, add esoteric
features, etc. The [6]FAQ contains a lot of information and solutions
to problems, but please feel free to [7]contact me if you have
problems or questions.
Background:
VNC (Virtual Network Computing) is a very useful network graphics
protocol (applications running on one computer but displaying their
windows on another) in the spirit of X, however, unlike X, the
viewing-end is very simple and maintains no state. It is a remote
framebuffer (RFB) protocol
Some VNC links:
* [8]http://www.uk.research.att.com/vnc/
* [9]http://www.realvnc.com
* [10]http://www.tightvnc.com
For Unix, the VNC implementation includes a virtual X11 server Xvnc
(usually launched via the vncserver command) that is not associated
with a physical display, but provides a "fake" one X11 clients (xterm,
mozilla, etc.) can attach to. A remote user then connects to Xvnc via
the VNC client vncviewer from anywhere on the network to view and
interact with the whole virtual X11 desktop.
The VNC protocol is in most cases better suited for remote connections
with low bandwidth and high latency than is the X11 protocol (the
exception is cached pixmap data on the viewing-end). Also, with no
state maintained the viewing-end can crash, be rebooted, or relocated
and the applications and desktop continue running. Not so with X11.
So the standard Xvnc/vncserver program is very useful, I use it for
things like:
* Desktop conferencing with other users (e.g. codereviews).
* Long running apps/tasks I want to be able to view from many
places.
* Motif, GNOME, and similar applications that would yield very poor
performance over a high latency link.
However, sometimes one wants to connect to a real X11 display (i.e.
one attached to a physical monitor, keyboard, and mouse: a Workstation
or a SunRay session) from far away. Maybe you want to close down an
application cleanly rather than using kill, or want to work a bit in
an already running application, or would like to help a distant
colleague solve a problem with their desktop. This is where x11vnc is
useful.
_________________________________________________________________
How to use x11vnc:
In this basic example let's assume the remote machine with the X
display you wish to view is "far-away.east:0" and the workstation you
are presently working at is "sitting-here.west".
Step 0. Download x11vnc ([11]see below) and have it available to run
on far-away.east. Similarly, have a VNC viewer (e.g. vncviewer) ready
to run on sitting-here.west. We recommend [12]TightVNC Viewers.
Step 1. By some means log in to far-away.east and get a command shell
running there. You can use ssh, rlogin, telnet, or any other method to
do this. x11vnc needs to be run on the same machine the X server
process is running on (otherwise things would be extremely slow).
Step 2. In that far-away.east shell (with command prompt "far-away>"
in this example) run x11vnc directed at the far-away.east X session
display:
far-away> x11vnc -display :0
You could have also set the environment variable DISPLAY=:0 instead of
using -display. This step attaches x11vnc to the far-away.east:0 X
display (i.e. no viewer clients yet).
To get X11 permissions right, you may also need to set the XAUTHORITY
environment variable (or use the [13]-auth option) to point to the
correct MIT-MAGIC-COOKIE file (e.g. /home/joe/.Xauthority). More on
this [14]below.
If you suspect an X11 permissions problem do this simple test: while
sitting at the physical X display open a terminal window
(gnome-terminal, xterm, etc). You should be able to start x11vnc
without any need for command line options in that terminal. If that
works OK then you know X11 permissions are the only thing preventing
it from working when you try to start x11vnc via a remote shell.
When x11vnc starts up there will then be much chatter printed out,
until it finally says something like:
.
.
13/05/2004 14:59:54 Autoprobing selected port 5900
13/05/2004 14:59:54 screen setup finished.
13/05/2004 14:59:54 The VNC desktop is far-away:0
PORT=5900
which means all is OK, and we are ready for the final step.
Step 3. At the place where you are sitting (sitting-here.west in this
example) you now want to run a VNC viewer program. There are VNC
viewers for Unix, Windows, MacOS, Java-enabled web browsers, and even
for PDA's like the Palm Pilot! You can use any of them to connect to
x11vnc (see the above VNC links under "Background:" on how to obtain a
viewer for your platform or see [15]this FAQ. For Solaris, vncviewer
is available in the [16]Companion CD package SFWvnc ).
In this example we'll use the Unix vncviewer program on sitting-here
by typing the following command in a second terminal window:
sitting-here> vncviewer far-away.east:0
That should pop up a viewer window on sitting-here.west showing and
allowing interaction with the far-away.east:0 X11 desktop. Pretty
nifty! When finished, exit the viewer: the remote x11vnc process will
shutdown automatically (or you can use the [17]-forever option to have
it wait for additional viewer connections).
Shortcut: Of course if you left x11vnc running on far-away.east:0 in a
terminal window with the [18]-forever option or as a [19]service,
you'd only have to do Step 3 as you moved around. Be sure to use a VNC
[20]password or [21]other measures if you do that.
Desktop Sharing: The above more or less assumed nobody was sitting at
the workstation display "far-away.east:0". This is often the case: a
user wants to access her workstation remotely. Another usage pattern
has the user sitting at "far-away.east:0" and invites one or more
other people to view and interact with his desktop. Perhaps the user
gives a demo or presentation this way (using the telephone for vocal
communication). A "Remote Help Desk" mode would be similar: a
technician remotely connects to the user's desktop to interactively
solve a problem the user is having.
For these cases it should be obvious how it is done. The above steps
will work, but more easily the user sitting at far-away.east:0 simply
starts up x11vnc from a terminal window, after which the guests would
start their VNC viewers. For this usage mode the "[22]-connect
host1,host2" option may be of use automatically connect to vncviewers
in "-listen" mode on the list of hosts.
_________________________________________________________________
Tunnelling x11vnc via ssh:
The above example had no security or privacy at all. When logging into
remote machines (certainly when going over the internet) it is best to
use ssh, or use a VPN. For x11vnc one can tunnel the VNC protocol
through the encrypted ssh channel. It would look something like this:
sitting-here> ssh -L 5900:localhost:5900 far-away.east 'x11vnc -display :0'
(you will likely have to provide passwords/passphrases for the ssh
login) and then in another terminal window on sitting-here run the
command:
sitting-here> vncviewer -encodings "copyrect tight zrle hextile" localhost:0
Note: The -encodings option is very important: vncviewer will default
to "raw" encoding if it thinks the connection is to the local machine,
and so vncviewer gets tricked this way by the ssh redirection. "raw"
encoding will be extremely slow over a networked link, so you need to
force the issue with -encodings "copyrect tight ...".
Some VNC viewers will do the ssh tunnelling for you automatically, the
TightVNC vncviewer does this when the "-via far-away.east" option is
supplied to it (this requires x11vnc to be already running on
far-away.east or having it started by [23]inetd(1)). See the 3rd
script example [24]below for more info.
If the machine you SSH into is not the same machine with the X display
you wish to view (e.g. your company provides incoming SSH access to a
gateway machine), then you need to change the above to, e.g.: "-L
5900:otherhost:5900". Once logged in, you'll need to do a second login
(ssh, rsh, etc.) to the workstation machine 'otherhost' and then start
up x11vnc on it if it isn't already running.
_________________________________________________________________
Scripts to automate ssh tunneling: As discussed below, there may be
some problems with port 5900 being available. If that happens, the
above port and display numbers may change a bit (e.g. -> 5901 and :1).
However, if you "know" port 5900 will be free on the local and remote
machines, you can easily automate the above two steps by using the
x11vnc option [25]-bg (forks into background after connection to the
display is set up) or using the -f option of ssh. Three example
scripts are shown below.
_________________________________________________________________
#1. A simple example script, assuming no problems with port 5900 being
taken on the local or remote sides, looks like:
#!/bin/sh
# usage: x11vnc_ssh <host>:<xdisplay>
# e.g.: x11vnc_ssh snoopy.peanuts.com:0
host=`echo $1 | awk -F: '{print $1}'`
disp=`echo $1 | awk -F: '{print $2}'`
if [ "x$disp" = "x" ]; then disp=0; fi
cmd="x11vnc -display :$disp -localhost -rfbauth .vnc/passwd"
enc="copyrect tight zrle hextile zlib corre rre raw"
ssh -f -L 5900:localhost:5900 $host "$cmd"
for i in 1 2 3
do
sleep 2
if vncviewer -encodings "$enc" :0; then break; fi
done
See also rx11vnc.pl below.
_________________________________________________________________
#2. Another method is to start the VNC viewer in listen mode
"vncviewer -listen" and have x11vnc initiate a reverse connection
using the [26]-connect option:
#!/bin/sh
# usage: x11vnc_ssh <host>:<xdisplay>
# e.g.: x11vnc_ssh snoopy.peanuts.com:0
host=`echo $1 | awk -F: '{print $1}'`
disp=`echo $1 | awk -F: '{print $2}'`
if [ "x$disp" = "x" ]; then disp=0; fi
cmd="x11vnc -display :$disp -localhost -connect localhost" # <== note new opt
ion
enc="copyrect tight zrle hextile zlib corre rre raw"
vncviewer -encodings "$enc" -listen &
pid=$!
ssh -R 5500:localhost:5500 $host "$cmd"
kill $pid
Note the use of the ssh option -R instead of -L to set up a remote
port redirection.
_________________________________________________________________
#3. A third way is specific to the TightVNC vncviewer special option
-via for gateways. The only tricky part is we need to start up x11vnc
and give it some time (5 seconds in this example) to start listening
for connections (so we cannot use the TightVNC default setting for
VNC_VIA_CMD):
#!/bin/sh
# usage: x11vnc_ssh <host>:<xdisplay>
# e.g.: x11vnc_ssh snoopy.peanuts.com:0
host=`echo $1 | awk -F: '{print $1}'`
disp=`echo $1 | awk -F: '{print $2}'`
if [ "x$disp" = "x" ]; then disp=0; fi
VNC_VIA_CMD="ssh -f -L %L:%H:%R %G x11vnc -localhost -rfbport 5900 -display :$d
isp; sleep 5"
export VNC_VIA_CMD
vncviewer -via $host localhost:0 # must be TightVNC vncviewer.
Of course if you already have the x11vnc running waiting for
connections (or have it started out of [27]inetd(1)), you can simply
use the TightVNC "vncviewer -via gateway host:port" in its default
mode to provide secure ssh tunnelling.
VNC password file: Also note in the #1. example script that the
[28]option "-rfbauth .vnc/passwd" provides additional protection by
requiring a VNC password for every VNC viewer that connects. The
vncpasswd or storepasswd programs, or the x11vnc [29]-storepasswd
option can be used to create the password file. x11vnc also has the
slightly less secure [30]-passwdfile and "-passwd XXXXX" [31]options
to specify passwords.
Important: It is up to you to tell x11vnc to use password protection,
it will not do it for you automatically or force you to. The same goes
for encrypting the channel between the viewer and x11vnc: it is up to
you to use ssh, stunnel, VPN, etc. Also look into the -allow and
-localhost [32]options and building x11vnc with [33]tcp_wrappers
support to limit host access.
_________________________________________________________________
Downloading x11vnc:
x11vnc is a contributed program to the [34]LibVNCServer project at
SourceForge.net. I use libvncserver for all of the VNC aspects; I
couldn't have done without it. The full source code may be found and
downloaded (either file-release tarball or CVS tree) from the above
link. As of Feb 2005, the [35]x11vnc-0.7.1.tar.gz source package is
released (recommended download) . The [36]x11vnc 0.7.1 release notes.
The x11vnc package is the subset of the libvncserver package needed to
build the x11vnc program. Also, you can get a copy of my latest,
bleeding edge [37]x11vnc.c file to replace the one in the above
packages or the one in the CVS tree and then rebuild. You can also
update the tcl/tk gui with the [38]tkx11vnc.h file. If you have an
older libvncserver source tree, you may need to switch on the OLD_TREE
variable near the top of the x11vnc.c file.
See the [39]FAQ below for information about where you might obtain a
precompiled x11vnc binary from 3rd parties.
To obtain VNC viewers for the viewing side (Windows, Mac OS, or Unix)
try these links:
* [40]http://www.tightvnc.com/download.html
* [41]http://www.realvnc.com/download-free.html
* [42]http://sourceforge.net/projects/cotvnc/
More tools: Here is a rsh/ssh wrapper script rx11vnc that attempts to
automatically do the above Steps 1-3 for you (provided you have
rsh/ssh login permission on the machine x11vnc is to be run on). The
above example would be: "rx11vnc far-away.east:0" typed into a shell
on sitting-here.west. Also included is an experimental script
rx11vnc.pl that attempts to tunnel the vnc traffic through an ssh port
redirection (and does not assume port 5900 is free). Have a look at
them to see what they do and customize as needed:
* [43]rx11vnc wrapper script
* [44]rx11vnc.pl wrapper script to tunnel traffic thru ssh
_________________________________________________________________
Building x11vnc:
If your OS has libjpeg.so and libz.so in standard locations you can
build as follows (example given for the 0.7.1 release of x11vnc:
replace with the version you downloaded):
(un-tar the x11vnc+libvncserver tarball)
# gzip -dc x11vnc-0.7.1.tar.gz | tar -xvf -
(cd to the source directory)
# cd x11vnc-0.7.1
(run configure and then run make)
# ./configure
# make
(if all went OK, copy x11vnc to the desired destination, e.g. $HOME/bin)
# cp ./x11vnc/x11vnc $HOME/bin
Or do make install, it will probably install to /usr/local/bin (run
./configure --help for information on customizing your configuration).
You can now run it via typing "x11vnc", "x11vnc -help", "x11vnc -nap
-display :0", etc.
Note: Currently gcc is required to build libvncserver. In some cases
it will build with non-gcc compilers, but the resulting binary often
fails to run properly. For Solaris pre-built gcc binaries are at
[45]http://www.sunfreeware.com/ However, one user reports it does
work fine when built with Sun Studio 10, so YMMV.
_________________________________________________________________
Building on Solaris, FreeBSD, etc: Depending on your version of
Solaris or other Unix OS the jpeg and/or zlib libraries may be in
non-standard places (e.g. /usr/local, /usr/sfw, /opt/sfw, etc).
Note: If configure cannot find these two libraries then TightVNC and
ZRLE encoding support will be disabled, and you don't want that! The
TightVNC encoding gives very good compression and performance, it even
makes a noticeable difference over a fast LAN.
Shortcuts: On Solaris 10 you can pick up almost everything just by
insuring that your PATH has /usr/sfw/bin (for gcc) and /usr/ccs/bin
(for other build tools), e.g.:
env PATH=/usr/sfw/bin:/usr/ccs/bin:$PATH sh -c './configure; make'
(The only thing this misses is /usr/X11/lib/libXrandr.so.2, which is
for the little used -xrandr option, see the script below to pick it up
as well).
libjpeg is included in Solaris 9 and later (/usr/sfw/include and
/usr/sfw/lib), and zlib in Solaris 8 and later (/usr/include and
/usr/lib). So on Solaris 9 you can pick up everything with something
like this:
env PATH=/usr/local/bin:/usr/ccs/bin:$PATH CPPFLAGS='-I /usr/sfw/include' LDF
LAGS='-L/usr/sfw/lib -R/usr/sfw/lib' sh -c './configure; make'
assuming your gcc is in /usr/local/bin. Or starting with the 0.7.1
x11vnc release:
env PATH=/usr/local/bin:/usr/ccs/bin:$PATH sh -c './configure --with-jpeg=/us
r/sfw; make'
These are getting pretty long, see those assignments split up in the
build script below.
If your system does not have these libraries at all you can get the
source for the libraries to build them: libjpeg is available at
[46]ftp://ftp.uu.net/graphics/jpeg/ and zlib at
[47]http://www.gzip.org/zlib/. See also
[48]http://www.sunfreeware.com/ for Solaris binary packages of these
libraries as well as for gcc. Normally they will install into
/usr/local but you can install them anywhere with the
--prefix=/path/to/anywhere, etc.
Here is a build script that indicates one way to pass the library
locations information to the libvncserver configuration via the
CPPFLAGS and LDFLAGS environment variables.
#!/bin/sh
# Build script for Solaris, etc, with gcc, libjpeg and libz in
# non-standard locations.
# set to get your gcc, etc:
#
PATH=/path/to/gcc/bin:/usr/ccs/bin:/usr/sfw/bin:$PATH
JPEG=/path/to/jpeg # set to maybe "/usr/local", "/usr/sfw", or "/opt/sfw"
ZLIB=/path/to/zlib # set to maybe "/usr/local", "/usr/sfw", or "/opt/sfw"
# Below we assume headers in $JPEG/include and $ZLIB/include and the
# shared libraries are in $JPEG/lib and $ZLIB/lib. If your situation
# is different change the locations in the two lines below.
#
CPPFLAGS="-I $JPEG/include -I $ZLIB/include"
LDFLAGS="-L $JPEG/lib -R $JPEG/lib -L $ZLIB/lib -R $ZLIB/lib"
# These two lines may not be needed on more recent Solaris releases:
#
CPPFLAGS="$CPPFLAGS -I /usr/openwin/include"
LDFLAGS="$LDFLAGS -L /usr/openwin/lib -R /usr/openwin/lib"
# These are for libXrandr.so on Solaris 10:
#
CPPFLAGS="$CPPFLAGS -I /usr/X11/include"
LDFLAGS="$LDFLAGS -L /usr/X11/lib -R /usr/X11/lib"
# Everything needs to built with _REENTRANT for thread safe errno:
#
CPPFLAGS="$CPPFLAGS -D_REENTRANT"
export PATH CPPFLAGS LDFLAGS
./configure
make
ls -l ./x11vnc/x11vnc
Then do make install or copy the x11vnc binary to your desired
destination.
BTW, To run a shell script, just cut-and-paste the above into a file,
say "myscript", then modify the "/path/to/..." items to correspond to
your system/environment, and then type: "sh myscript" to run it.
Note that on Solaris make is /usr/ccs/bin/make, so that is why the
above puts /usr/ccs/bin in PATH. Other important build utilities are
there too: ld, ar, etc. Also, it is probably a bad idea to have
/usr/ucb in your PATH while building.
Starting with the 0.7.1 x11vnc release the "configure --with-jpeg=DIR
--with-zlib=DIR" options are handy if you want to avoid making a
script.
One user had a problem where the above build script was failing
because his work environment had the ENV variable set to a script that
was resetting his PATH so that gcc could no longer be found. Make sure
you do not have any ENV or BASH_ENV in your environment doing things
like that.
If you need to build on Solaris 2.5.1 or earlier or other older Unix
OS's, see [49]this workaround FAQ.
Building on FreeBSD, OpenBSD, ...: The jpeg libraries seem to be in
/usr/local or /usr/pkg on these OS's. You won't need the openwin stuff
in the above script (but you may need /usr/X11R6/...). Also starting
with the 0.7.1 x11vnc release, this usually works:
./configure --with-jpeg=/usr/local
make
Building on HP-UX: For jpeg and zlib you will need to do the same
sort of thing as described above for Solaris. You set CPPFLAGS and
LDFLAGS to find them (see below for an example). You do not need to do
any of the above /usr/openwin stuff. Also, HP-UX does not seem to
support -R, so get rid of the -R items in LDFLAGS. Because of this, at
runtime you may need to set LD_LIBRARY_PATH or SHLIB_PATH to indicate
the directory paths so the libraries can be found. It is a good idea
to have static archives, e.g. libz.a and libjpeg.a for the nonstandard
libraries so that they get bolted into the x11vnc binary.
Finally, there seems to be a bug with configure on HP-UX 11.xx: it
thinks it cannot find gettimeofday(). As a workaround add this to
CPPFLAGS: -DLIBVNCSERVER_HAVE_GETTIMEOFDAY=1. You may get some
warnings but we have verified that this generates working x11vnc
binaries on HP-UX hppa and ia64. (This problem will be fixed in
version 0.7.2 by using a newer autoconf).
Here is what we recently did to build x11vnc 0.7.1 on HP-UX 11.11
env CPPFLAGS="-DLIBVNCSERVER_HAVE_GETTIMEOFDAY=1 -I $HOME/hpux/jpeg/include -I
$HOME/hpux/zlib/include" LDFLAGS="-L $HOME/hpux/jpeg/lib -L $HOME/hpux/zlib/lib
" ./configure
make
Where we had static archives (libjpeg.a, libz.a) only in the
$HOME/hpux/... directories.
_________________________________________________________________
Beta Testing:
I don't have any formal beta-testers for the releases of x11vnc, so
I'd appreciate any additional testing very much!
I'd like to release version 0.7.2 in Apr/May 2005 sometime, here is
the current tarball: [50]x11vnc-0.7.2.tar.gz. Please kick the tires,
and report bugs, performance regressions, etc. to [51]me.
Here is what is shaping up to be [52]the release notes for 0.7.2..
Note that the [53]X DAMAGE feature will be on by default and so I am
interested if that causes any problems. I'd also like to have the new
"wireframe" move/resize stuff, the "wireframe copyrect", and the
"scroll detection copyrect" all on by default as well! The scroll
copyrect is currently the least stable, you can toggle it off via
"-noscr". Let me know of any issues you find for any of these new
features. Thanks!
_________________________________________________________________
Some Notes:
Both a client and a server: It is sometimes confusing to people that
x11vnc is both a client and a server at the same time. It is an X
client because it connects to the running X server to do the screen
polls. Think of it as a rather efficient "screenshot" program running
continuously. It is a server in the sense that it is a VNC server VNC
viewers on the network can connect to and view the screen framebuffer
it manages.
When trying to debug problems, remember to think of both roles. E.g.
"how is x11vnc connecting to the X server?", "how is the vncviewer
connecting to x11vnc?", "what permits/restricts the connection?". Both
links may have reachability, permission, and other issues.
Network performance: Whether you are using Xvnc or x11vnc it is
always a good idea to have a solid background color instead of a
pretty background image. Each and every re-exposure of the background
must be resent over the network: better to have that background be a
solid color that compresses very well compared to a photo image. (This
is one place where the X protocol has an advantage over the VNC
protocol.) I suggest using xsetroot, dtstyle or similar utility to set
a solid background while using x11vnc. You can turn the pretty
background image back on when you are using the display directly.
Update: As of Feb/2005 in the libvncserver CVS, x11vnc has the
[54]-solid [color] option that works on recent GNOME, KDE, and CDE and
also on classic X (background image is on the root window).
I also find the [55]TightVNC encoding gives the best response for my
usage (Unix <-> Unix over cable modem). One needs a tightvnc-aware
vncviewer to take advantage of this encoding.
TCP port issues: Notice the lines
18/07/2003 14:36:31 Autoprobing selected port 5900
PORT=5900
in the output. 5900 is the default VNC listening port (just like 6000
is X11's default listening port). Had port 5900 been taken by some
other application, x11vnc would have next tried 5901. That would mean
the viewer command above should be changed to vncviewer
far-away.east:1. You can force the issue with the "[56]-rfbport NNNN"
option where NNNN is the desired port number. If that port is already
taken, x11vnc will exit immediately. (also see the "SunRay Gotcha"
note below)
Options: x11vnc has (far too) many features that may be activated
via its [57]command line options. Useful options are, e.g., -scale to
do server-side scaling, and -rfbauth passwd-file to use VNC password
protection (the vncpasswd or storepasswd programs, or the x11vnc
[58]-storepasswd option can be used to create the password file).
Algorithm: How does x11vnc do it? Rather brute-forcedly: it
continuously polls the X11 framebuffer for changes using
XShmGetImage(). When changes are discovered, it instructs libvncserver
which rectangular regions of the framebuffer have changed, and
libvncserver compresses the changes and sends them off to any
connected VNC viewers. A number of applications do similar things,
such as x0rfbserver, krfb, x0vncserver, vino. x11vnc uses a 32 x 32
pixel tile model (the desktop is decomposed into roughly 1000 such
tiles), where changed tiles are found by pseudo-randomly polling 1
pixel tall horizontal scanlines. This is a surprisingly effective
algorithm for finding changed regions. For keyboard and mouse user
input the XTEST extension is used to pass the input events to the X
server. To detect XBell "beeps" the XKEYBOARD extension is used. If
available, the XFIXES extension is used to retrieve the current mouse
cursor shape. Also, if available the X DAMAGE extension is used to
receive hints from the X server where modified regions on the screen
are. This greatly reduces the system load when not much is changing on
the screen and also improves how quickly the screen is updated.
Barbershop mirrors effect: What if x11vnc is started up, and
vncviewer is then started up on the same machine and displayed on the
same display x11vnc is polling? One might "accidentally" do this when
first testing out the programs. You get an interesting "feedback"
effect where vncviewer images keep popping up each one contained in
the previous one and slightly shifted a bit by the window manager
decorations. There will be an [59]even more interesting effect if
-scale is used. Also, if the XKEYBOARD is supported and the XBell
"beeps" once, you get an infinite loop of beeps going off. Although
all of this is mildly exciting it is not much use: you will normally
run and display the viewer on a different machine!
SunRay notes: You can run x11vnc on your (connected or disconnected)
[60]SunRay session (Please remember to use [61]-nap and maybe
[62]-wait 200 to avoid being a resource hog! It also helps to have a
solid background color). You have to know the name of the machine your
SunRay session X server is running on. You also need to know the X11
DISPLAY number for the session: on a SunRay it could be a large
number, e.g. :137, since there are many people with X sessions (Xsun
processes) on the same machine. If you don't know it, you can get it
by running who(1) in a shell on the SunRay server and looking for the
dtlocal entry with your username (and if you don't even know which
server machine has your session, you could login to all possible ones
looking at the who output for your username...).
I put some code in my ~/.xsession script that stores $DISPLAY in my
~/.sunray_current file at session startup and deletes it when the
session ends to make it easy to get at the hostname and X11 display
number info for my current X sessions.
SunRay Gotcha #1: Note that even though your SunRay X11 DISPLAY is
something like :137, x11vnc still tries for port 5900 as its listening
port if it can get it, in which case the VNC display (i.e. the
information you supply to the VNC viewer) is something like
sunray-server:0 (note the :0 corresponding to port 5900, it is not
:137). If it cannot get 5900, it tries for 5901, and so on. You can
also try to force the port (and thereby the VNC display) using the
[63]-rfbport NNNN option.
SunRay Gotcha #2: If you get an error like:
shmget(tile) failed.
shmget: No space left on device
when starting up x11vnc that most likely means all the shared memory
(shm) slots are filled up on your machine. The Solaris default is only
100, and that can get filled up in a week or so on a SunRay server
with lots of users. If the shm slot is orphaned (e.g. creator process
dies) the slot is not reclaimed. You can view the shm slots with the
"ipcs -mA" command. If there are about 100 then you've probably hit
this problem. They can be cleaned out (by the owner or by root) using
the ipcrm command. I wrote a script [64]shm_clear that finds the
orphans and lists or removes them. Longer term, have your SunRay
sysadmin add something like this to /etc/system:
set shmsys:shminfo_shmmax = 0x2000000
set shmsys:shminfo_shmmni = 0x1000
Limitations:
* Due to the polling nature, some activities (opaque window moves,
scrolling), can be pretty choppy/ragged and others (exposures of
large areas) slow. Experiment with interacting a bit differently
than you normally do to minimize the effects (e.g. do fullpage
paging rather than line-by-line scrolling, and move windows in a
single, quick motion). Work is in progress to attempt to speed
things up using the copyrect encoding and other things, but they
will likely only speed up certain activities, not all.
* A rate limiting factor for x11vnc performance is that video
hardware is optimized for writing, not reading (x11vnc reads the
video framebuffer for the screen image data). The difference can
be a factor of 10 to 1000, and so it usually takes about 0.5-1 sec
to read in the whole video hardware framebuffer (e.g. 5MB for
1280x1024 at depth 24). So whenever activity changes most of the
screen (e.g. moving or iconifying a large window) there is a delay
of 0.5-1 sec while x11vnc reads the changed regions in.
To get a sense of the read and write speeds of your video card,
you can run the benchmarks like: x11perf -getimage500, x11perf
-putimage500, x11perf -shmput500 and for XFree86 displays with
direct graphics access the dga command (press "b" to run the
benchmark and then after a few seconds press "q" to quit). Even
this "dd if=/dev/fb0 of=/dev/null" often gives a good estimate.
On XFree86 it is actually possible to increase the framebuffer
read speed considerably (5-100 times) by using the Shadow
Framebuffer (a copy of the framebuffer is kept in main memory and
this can be read much more quickly). To do this one puts the line
Option "ShadowFB" "true" (and depending on video card driver,
Option "NoAccel" "true" may be needed too) in the Device section
of the /etc/X11/XF86Config file. Note that this disables 2D
acceleration at the physical display and so likely defeats the
purpose. Nevertheless this could be handy in some circumstances,
e.g. if the slower speed while sitting at the physical display was
acceptable (this seems to be true for most video cards these
days). Unfortunately it does not seem shadowfb can be turned on
and off dynamically...
Another amusing thing one can do is use Xvfb as the X server, e.g.
"xinit $HOME/.xinitrc -- /usr/X11R6/bin/Xvfb :1 -screen 0
1024x768x16" x11vnc can poll Xvfb efficiently via main memory.
It's not exactly clear why one would want to do this (perhaps to
take advantage of an x11vnc feature, such as framebuffer scaling),
instead of using vncserver/Xvnc, but we mention it because it may
be of use for special purpose applications.
* Somewhat surprisingly, the X11 mouse (cursor) shape is write-only
and cannot be queried from the X server. So in x11vnc the cursor
shape stays fixed at an arrow. (see the "-cursor X" and "-cursor
some" [65]options, however, for a partial hack for the root
window, etc.). Also, on Solaris using the SUN_OVL overlay
extension, x11vnc can show the correct mouse cursor when the
[66]-overlay option is also supplied. A similar thing is done on
IRIX as well when -overlay is supplied. As of Dec/2004 x11vnc
supports the XFIXES extension (in Xorg and Solaris 10) to query
the X server for the exact cursor shape, this works pretty well
except that cursors with transparency (alpha channel) need to
approximated to solid RGB values.
* Audio from applications is of course not redirected (separate
redirectors do exist, e.g. esd). The XBell() "beeps" will work if
the X server supports the XKEYBOARD extension. (Note that on
Solaris XKEYBOARD is disabled by default. Passing +kb to Xsun
enables it).
* Occasionally a patch of tiles will not get updated correctly.
Evidently a timing related bug and difficult to reproduce...
* Using -threads can expose some bugs in libvncserver.
Please feel free to [67]contact me if you have any questions,
problems, or comments about x11vnc, etc.
Also, some people ask if they can make a donation, see [68]this link
for that.
_________________________________________________________________
x11vnc FAQ:
[Building and Starting]
[69]Q-1: I can't get x11vnc to start up. It says "XOpenDisplay failed
(null)" or "Xlib: connection to ":0.0" refused by server Xlib: No
protocol specified" and then exits. What do I need to do?
[70]Q-2: I can't get x11vnc and/or libvncserver to compile.
[71]Q-3: I just built x11vnc successfully, but when I use it my
keystrokes and mouse button clicks are ignored (I am able to move the
mouse though).
[72]Q-4: Help, I need to run x11vnc on Solaris 2.5.1 (or other old
Unix/Linux) and it doesn't compile!
[73]Q-5: Where can I get a precompiled x11vnc binary for my Operating
System?
[74]Q-6: Where can I get a VNC Viewer binary (or source code) for the
Operating System I will be viewing from?
[75]Q-7: How can I see all of x11vnc's command line options and
documentation on how to use them?
[76]Q-8: I don't like typing arcane command line options every time I
start x11vnc. What can I do? Is there a config file? Or a GUI?
[77]Q-9: Can I make x11vnc more quiet and also go into the background
after starting up?
[78]Q-10: Sometimes when a VNC viewer dies abruptly, x11vnc also dies
with the error message like: "Broken pipe". I'm using the -forever
mode and I want x11vnc to keep running.
[79]Q-11: Are there any build-time customizations possible, e.g.
change defaults, create a smaller binary, etc?
[Win2VNC Related]
[80]Q-12: I have two separate machine displays in front of me, one
Windows the other X11: can I use x11vnc in combination with Win2VNC in
dual-screen mode to pass the keystrokes and mouse motions to the X11
display?
[81]Q-13: I am running Win2VNC on my Windows machine and "x11vnc
-nofb" on Unix to pass keyboard and mouse to the Unix monitor.
Whenever I start Win2VNC it quickly disconnects and x11vnc says:
rfbProcessClientNormalMessage: read: Connection reset by peer
[Color Issues]
[82]Q-14: The X display I run x11vnc on is only 8 bits per pixel (bpp)
PseudoColor (i.e. only 256 distinct colors). The x11vnc colors may
start out OK, but after a while they are incorrect in certain windows.
[83]Q-15: Color problems: Why are the colors for some windows messed
up in x11vnc? BTW, my X display has nice overlay/multi-depth visuals
of different color depths: e.g. there are both depth 8 and 24 visuals
available at the same time.
[84]Q-16: How do I figure out the window id to supply to the -id
windowid option?
[85]Q-17: Why don't menus or other transient windows come up when I am
using the -id windowid option to view a single application window?
[86]Q-18: My X display is depth 24 at 24bpp (instead of the normal
depth 24 at 32bpp). I'm having lots of color and visual problems with
x11vnc and/or vncviewer. What's up?
[Xterminals]
[87]Q-19: Can I use x11vnc to view and interact with an Xterminal
(e.g. NCD) that is not running UNIX and so x11vnc cannot be run on it
directly?
[88]Q-20: How do I get my X permissions (MIT-MAGIC-COOKIE) correct for
a Unix/Linux machine acting as an Xterminal?
[Remote Control]
[89]Q-21: How do I stop x11vnc once it is running in the background?
[90]Q-22: Can I change settings in x11vnc without having to restart
it? Can I remote control it?
[Security and Permissions]
[91]Q-23: How do I create a VNC password for use with x11vnc?
[92]Q-24: Can I have two passwords for VNC viewers, one for full
access and the other for view-only access to the display?
[93]Q-25: Can I fine tune what types of user input are allowed? E.g.
have some users just be able to move the mouse, but not click or type
anything?
[94]Q-26: Why does x11vnc exit as soon as the VNC viewer disconnects?
And why doesn't it allow more than one VNC viewer to connect at the
same time?
[95]Q-27: Can I limit which machines incoming VNC clients can connect
from?
[96]Q-28: How do I build x11vnc/libvncserver with libwrap
(tcp_wrappers) support?
[97]Q-29: Can I have x11vnc only listen on one network interface (e.g.
internal LAN) rather than having it listen on all network interfaces
and relying on -allow to filter unwanted connections out?
[98]Q-30: Now that -localhost implies listening only on the loopback
interface, how I can occasionally allow in a non-localhost via the
allowonce remote control command?
[99]Q-31: How can I tunnel my connection to x11vnc via an encrypted
SSH channel between two Unix machines?
[100]Q-32: How can I tunnel my connection to x11vnc via an encrypted
SSH channel from Windows using an SSH client like Putty?
[101]Q-33: Can I prompt the user at the local X display whether the
incoming VNC client should be accepted or not? Can I decide to make
some clients view-only? How about running an arbitrary program to make
the decisions?
[102]Q-34: Does x11vnc support Unix usernames and passwords? Can I
further limit the set of Unix usernames who can connect to the VNC
desktop?
[103]Q-35: I start x11vnc as root because it is launched via inetd(1)
or a display manager like gdm(1). Can I have x11vnc later switch to a
different user?
[104]Q-36: I use a screen-lock when I leave my workstation (e.g.
xscreensaver or xlock). When I remotely access my workstation desktop
via x11vnc I can unlock the desktop fine, but I am worried people will
see my activities on the physical monitor. What can I do to prevent
this, or at least make it more difficult?
[105]Q-37: Can I have x11vnc automatically lock the screen when I
disconnect the VNC viewer?
[Display Managers and Services]
[106]Q-38: How can I run x11vnc as a "service" that is always
available?
[107]Q-39: How can I use x11vnc to connect to an X login screen like
xdm, GNOME gdm, KDE kdm, or CDE dtlogin? (i.e. nobody is logged into
an X session yet).
[108]Q-40: Can I run x11vnc out of inetd(1)? How about xinetd(1)?
[109]Q-41: How do I make x11vnc work with the Java VNC viewer applet
in a web browser?
[110]Q-42: Are reverse connections (i.e. the VNC server connecting to
the VNC viewer) using "vncviewer -listen" and vncconnect(1) supported?
[111]Q-43: Can I use x11vnc as a replacement for Xvnc? (i.e. not for a
real display, but for a virtual one I keep around).
[112]Q-44: How can I use x11vnc on "headless" machines? Why might I
want to?
[Resource Usage and Performance]
[113]Q-45: I have lots of memory, but why does x11vnc fail with
shmget: No space left on device or Minor opcode of failed
request: 1 (X_ShmAttach)?
[114]Q-46: How can I make x11vnc use less system resources?
[115]Q-47: How can I make x11vnc use MORE system resources?
[116]Q-48: I use x11vnc over a slow link with high latency (e.g.
dialup modem), is there anything I can do to speed things up?
[117]Q-49: When I drag windows around with the mouse or scroll up and
down things really bog down (unless I do the drag in a single, quick
motion). Is there anything to do to improve things?
[118]Q-50: Why not do something like wireframe animations to avoid the
windows "lurching" when being moved or resized?
[119]Q-51: Does x11vnc support the X DAMAGE Xserver extension to find
modified regions of the screen quickly and efficiently?
[Mouse Cursor Shapes]
[120]Q-52: Why isn't the mouse cursor shape (the little icon shape
where the mouse pointer is) correct as I move from window to window?
[121]Q-53: When using XFIXES cursorshape mode, some of the cursors
look really bad with extra black borders around the cursor and other
cruft. How can I improve their appearance?
[122]Q-54: In XFIXES mode, are there any hacks to handle cursor
transparency ("alpha channel") exactly?
[Mouse Pointer]
[123]Q-55: Why does the mouse arrow just stay in one corner in my
vncviewer, whereas my cursor (that does move) is just a dot?
[124]Q-56: Can I take advantage of the TightVNC extension to the VNC
protocol where Cursor Positions Updates are sent back to all connected
clients (i.e. passive viewers can see the mouse cursor being moved
around by another viewer)?
[125]Q-57: Is it possible to swap the mouse buttons (e.g. left-handed
operation), or arbitrarily remap them? How about mapping button clicks
to keystrokes, e.g. to partially emulate Mouse wheel scrolling?
[Keyboard Issues]
[126]Q-58: How can I get my AltGr and Shift modifiers to work between
keyboards for different languages?
[127]Q-59: When I try to type a "<" (i.e. less than) instead I get ">"
(i.e. greater than)! Strangely, typing ">" works OK!!
[128]Q-60: I'm using an "international" keyboard (e.g. German "de", or
Danish "dk") and the -modtweak mode works well if the VNC viewer is
run on a Unix/Linux machine with a similar keyboard. But if I run
the VNC viewer on Unix/Linux with a different keyboard (e.g. "us") or
Windows with any keyboard, I can't type some keys like: "@", "$",
"<", ">", etc. How can I fix this?
[129]Q-61: When typing I sometimes get double, triple, or more of my
keystrokes repeated. I'm sure I only typed them once, what can I do?
[130]Q-62: The x11vnc -norepeat mode is in effect, but I still get
repeated keystrokes!!
[131]Q-63: The machine where I run x11vnc has an AltGr key, but the
local machine where I run the VNC viewer does not. Is there a way I
can map a local unused key to send an AltGr? How about a Compose key
as well?
[132]Q-64: I have a Sun machine I run x11vnc on. Its Sun keyboard has
just one Alt key labelled "Alt" and two Meta keys labelled with little
diamonds. The machine where I run the VNC viewer only has Alt keys.
How can I send a Meta keypress? (e.g. emacs needs this)
[133]Q-65: Can I map a keystroke to a mouse button click on the remote
machine?
[Screen Related Issues and Features]
[134]Q-66: The remote display is larger (in number of pixels) than the
local display I am running the vncviewer on. I don't like the
vncviewer scrollbars, what I can do?
[135]Q-67: Does x11vnc support server-side framebuffer scaling? (E.g.
to make the desktop smaller).
[136]Q-68: Does x11vnc work with Xinerama? (i.e. multiple monitors
joined together to form one big, single screen).
[137]Q-69: Can I use x11vnc on a multi-headed display that is not
Xinerama (i.e. separate screens :0.0, :0.1, ... for each monitor)?
[138]Q-70: Can x11vnc show only a portion of the display? (E.g. for a
special purpose rfb application).
[139]Q-71: Does x11vnc support the XRANDR (X Resize, Rotate and
Reflection) extension? Whenever I rotate or resize the screen x11vnc
just seems to crash.
[140]Q-72: Why is the view in my VNC viewer completely black? Or why
is everything flashing around randomly?
[141]Q-73: I use Linux Virtual Consoles (VC's) to implement 'Fast User
Switching' between users' sessions (e.g. Betty is on Ctrl-Alt-F7,
Bobby is on Ctrl-Alt-F8, and Sid is on Ctrl-Alt-F1: they use those
keystrokes to switch between their sessions). How come the view in a
VNC viewer connecting to x11vnc is either completely black or
otherwise all messed up unless the X session x11vnc is attached to is
in the active VC?
[142]Q-74: Can I use x11vnc to view my VMWare session remotely?
[143]Q-75: Can non-X devices (e.g. a raw framebuffer) be viewed and/or
controlled by x11vnc?
[144]Q-76: I am using x11vnc where my local machine has "popup/hidden
taskbars" (e.g. GNOME or MacOS X) and the remote display where x11vnc
runs also has "popup/hidden taskbars" (e.g. GNOME). When I move the
mouse to the edge of the screen where the popups happen, the taskbars
interfere and fight with each other in strange ways. What can I do?
[Misc: Clipboard, Beeps, Thanks, etc.]
[145]Q-77: Does the Clipboard/Selection get transferred between the
vncviewer and the X display?
[146]Q-78: Why don't I hear the "Beeps" in my X session (e.g. when
typing tput bel in an xterm)?
[147]Q-79: Thanks for your program and for your help! Can I make a
donation?
_________________________________________________________________
[Building and Starting]
Q-1: I can't get x11vnc to start up. It says "XOpenDisplay failed
(null)" or "Xlib: connection to ":0.0" refused by server Xlib: No
protocol specified" and then exits. What do I need to do?
For the former error, you need to specify the X display to connect to
(it also needs to be on the same machine x11vnc is to run on). Set
your DISPLAY environment variable or use the [148]-display option to
specify it. Nearly always the correct value will be ":0"
For the latter error, you need to set up the X11 permissions
correctly.
To make sure X11 permissions are the problem do this simple test:
while sitting at the physical X display open a terminal window
(gnome-terminal, xterm, etc). You should be able to start x11vnc
without any need for special steps or command line options in that
terminal. If that works OK then you know X11 permissions are the only
thing preventing it from working when you try to start x11vnc via,
say, a remote shell.
How to Solve: See the xauth(1), Xsecurity(7), and xhost(1) man pages
for much info on X11 permissions. For example, you may need to set
your XAUTHORITY environment variable or use the [149]-auth option to
point to the correct cookie file (e.g. /home/joe/.Xauthority or
/var/gdm/:0.Xauth), or simply be sure you run x11vnc as the correct
user (i.e. the user who owns the X session you wish to view). Running
x11vnc as root is not enough: you need to know where the XAUTHORITY
file for the desired X display is. Example:
x11vnc -display :0 -auth /var/gdm/:0.Xauth
Less safe, but to avoid figuring out where the XAUTHORITY file is, if
the person sitting at the X session types "xhost +localhost" then one
should be able to attach x11vnc to the session (from the same
machine). The person could then type "xhost -localhost" after x11vnc
has connected to go back to the default permissions. Also, for some
situations the "-users lurk=" option may be of use (please read the
documentation on the [150]-users option).
To test out your X11 permissions from a remote shell, set DISPLAY and
possibly XAUTHORITY (see your shell's man page, bash(1), tcsh(1), on
how to set environment variables) and type xdpyinfo in the same place
you will be typing (or otherwise running) x11vnc. If information is
printed out about the X display (screen sizes, supported extensions,
color visuals info) that means the X11 permissions are set up
properly: xdpyinfo successfully connected to DISPLAY! You could also
type xclock and make sure no errors are reported (a clock should
appear on the X display, press Ctrl-C to stop it). If these work, then
typing "x11vnc" should also work.
Important: if you cannot get your X11 permissions so that the xdpyinfo
or xclock tests work, x11vnc also will not work (all of these X
clients must be allowed to connect to the X server to function
properly).
Q-2: I can't get x11vnc and/or libvncserver to compile.
Make sure you have all of the required -devel packages installed.
These include X11/XFree86, libjpeg, libz, ...
After running the libvncserver configure, carefully examine the output
and the messages in the config.log file looking for missing
components. If the configure output looks like:
checking how to run the C preprocessor... gcc -E
checking for X... no
checking for XkbSelectEvents in -lX11... no
checking for XineramaQueryScreens in -lXinerama... no
checking for XTestFakeKeyEvent in -lXtst... no
there is quite a bit wrong with the build environment. Hopefully
simply adding -devel packages will fix it.
For Debian the list seems to be:
gcc
make
libc6-dev
libjpeg62-dev
libx11-dev
libxext-dev
libxrandr-dev
libxtst-dev
x-dev
xlibs-static-dev
zlib1g-dev
For Redhat the list seems to be:
gcc
make
glibc-devel
libjpeg-devel
XFree86-devel
zlib-devel
Q-3: I just built x11vnc successfully, but when I use it my keystrokes
and mouse button clicks are ignored (I am able to move the mouse
though).
This is most likely due to you not having a working build environment
for the XTEST client library libXtst.so. The library is probably
present on your system, but the package installing the development
header file is missing.
If you were watching carefully while configure was running you would
have seen:
checking for XTestFakeKeyEvent in -lXtst... no
The solution is to add the necessary build environment package (and
the library package if that is missing too). On Debian the build
package is libxtst-dev. Other distros/OS's may have it in another
package.
x11vnc will build without support for this library (e.g. perhaps one
wants a view-only x11vnc on a stripped down or embedded system...). At
runtime it will also continue to run even if the X server it connects
to does not support XTEST. In both cases it cannot inject keystrokes
or button clicks since XTEST is needed for that (it can still move the
mouse pointer using the X API XWarpPointer()).
You will see a warning message something like this at run time:
20/03/2005 22:33:09 WARNING: XTEST extension not available (either missing fr
om
20/03/2005 22:33:09 display or client library libXtst missing at build time
).
20/03/2005 22:33:09 MOST user input (pointer and keyboard) will be DISCARDE
D.
20/03/2005 22:33:09 If display does have XTEST, be sure to build x11vnc wit
h
20/03/2005 22:33:09 a working libXtst build environment (e.g. libxtst-dev,
20/03/2005 22:33:09 or other packages).
20/03/2005 22:33:09 No XTEST extension, switching to -xwarppointer mode for
20/03/2005 22:33:09 pointer motion input.
Q-4: Help, I need to run x11vnc on Solaris 2.5.1 (or other old
Unix/Linux) and it doesn't compile!
We apologize that x11vnc does not build cleanly on older versions of
Solaris, Linux, etc.: very few users are on these old releases.
We have heard that since Dec/2004 a Solaris 2.6 built x11vnc will run
on Solaris Solaris 2.5 and 2.5.1 (since a workaround for XConvertCase
is provided).
In any event, here is a workaround for Solaris 2.5.1 (and perhaps
earlier and perhaps non-Solaris):
First use the environment settings (CPPFLAGS, LDFLAGS, etc.) in the
above [151]Solaris build script to run the configure command. That
should succeed without failure. Then you have to hand edit the
autogenerated rfb/rfbconfig.h file in the source tree, and just before
the last #endif at the bottom of that file insert these workaround
lines:
struct timeval _tmp_usleep_tv;
#define usleep(x) \
_tmp_usleep_tv.tv_sec = (x) / 1000000; \
_tmp_usleep_tv.tv_usec = (x) % 1000000; \
select(0, NULL, NULL, NULL, &_tmp_usleep_tv);
int gethostname(char *name, int namelen);
long random();
int srandom(unsigned int seed);
#undef LIBVNCSERVER_HAVE_LIBPTHREAD
#define SHUT_RDWR 2
typedef unsigned int in_addr_t;
#define snprintf(a, n, args...) sprintf((a), ## args)
Then run make with the Solaris build script environment, everything
should compile without problems, and the resulting x11vnc binary
should work OK. If some non-x11vnc related programs fail (e.g. test
programs) and the x11vnc binary is not created try "make -k" to have
it keep going. Similar sorts of kludges in rfb/rfbconfig.h can be done
on other older OS (Solaris, Linux, ...) releases.
Here are some notes for similar steps that need to be done to build on
[152]SunOS 4.x
Please let us know if you had to use the above workaround (and whether
it worked or not). If there is enough demand we will try to push clean
compilations back to earlier Solaris, Linux, etc, releases.
Q-5: Where can I get a precompiled x11vnc binary for my Operating
System?
Hopefully the [153]build steps above and [154]FAQ provide enough info
for a painless compile for most environments. Please report problems
with the x11vnc configure, make, etc. on your system (if your system
is known to compile other GNU packages successfully).
There are precompiled x11vnc binaries built by other groups that are
available at the following locations:
Debian: (.deb) [155]http://packages.debian.org/x11vnc
Slackware: (.tgz) [156]http://www.linuxpackages.net/ Redhat/Fedora:
(.rpm) [157]http://dag.wieers.com/packages/x11vnc/ SuSE: (.rpm)
[158]http://linux01.gwdg.de/~pbleser/ Solaris: (pkg)
[159]http://www.sunfreeware.com/ wwexptools: (.tgz)
[160]http://www.bell-labs.com/project/wwexptools/packages.html The
last one, wwexptools, provides a variety of Unix binaries (Linux,
Solaris, HP-UX, IRIX, ...) with the intent of being compatible on a
wide range of OS releases. Find x11vnc near the bottom of that page
and select 'download info'.
Note: it appears some of the wwexptools x11vnc binaries are not
compiled with libz and libjpeg and so the fast compression encodings:
"Tight", "ZRLE", etc are not supported by those binaries. You can see
this by looking at the x11vnc output and if it says the encoding for a
client is "hextile" then likely the fast compression encodings are
missing. If you want optimal performance on your OS, you should see
the [161]build notes above for where to download libz and libjpeg, and
then build everything with gcc. For Solaris, the
http://www.sunfreeware.com/ packages are built with libz and libjpeg.
If the above binaries don't work and building x11vnc on your OS fails
(and all else fails!) you can try one of my motley collection of
[162]test binaries. Some may be old, some may have extra debugging
output, etc. One of them may work on your OS...
As a general note, the x11vnc program is simple enough you don't
really need to install a package: the binary will in most cases work
as is and from any location (as long as your system libraries are not
too old, etc). So, for Linux distributions that are not one of the
above, the x11vnc binary from the above packages has a good chance of
working. You can "install" it by just copying the x11vnc binary to the
desired directory in your PATH. Tip on extracting files from a Debian
package: extract the archive via a command like: "ar x
x11vnc_0.6-2_i386.deb" and then you can find the binary in the
resulting data.tar.gz tar file. Also, rpm2cpio(1) is useful in
extracting files from rpm packages.
Q-6: Where can I get a VNC Viewer binary (or source code) for the
Operating System I will be viewing from?
To obtain VNC viewers for the viewing side (Windows, Mac OS, or Unix)
try here:
* [163]http://www.tightvnc.com/download.html
* [164]http://www.realvnc.com/download-free.html
* [165]http://sourceforge.net/projects/cotvnc/
Q-7: How can I see all of x11vnc's command line options and
documentation on how to use them?
Run: x11vnc -opts to list just the option names or run: x11vnc
-help for long descriptions about each option. The output is listed
[166]here as well.
Q-8: I don't like typing arcane command line options every time I
start x11vnc. What can I do? Is there a config file? Or a GUI?
You could create a shell script that calls x11vnc with your options:
#!/bin/sh
#
# filename: X11vnc (i.e. not "x11vnc")
# It resides in a directory in $PATH. "chmod 755 X11vnc" has been run on it.
#
x11vnc -nap -wait 50 -localhost -rfbauth $HOME/.vnc/passwd -display :0 $*
a similar thing can be done via aliases in your shell (bash, tcsh,
csh, etc..).
Or as of Jun/2004 in the libvncserver CVS you can use the simple
$HOME/.x11vncrc config file support. If that file exists, each line is
taken as a command line option. E.g. the above would be:
# this is a comment in my ~/.x11vncrc file
nap
wait 50 # this is a comment to the end of the line.
-localhost # note: the leading "-" is optional.
rfbauth /home/fred/.vnc/passwd
display :0
At some point this config file support will be expanded.
As of Dec/2004 in the libvncserver CVS there is now a simple tcl/tk
GUI based on the remote-control functionality that was added. It's not
particularly user-friendly, it just provides a point and click mode to
set all the many x11vnc parameters and obtain help on them. See the
[167]-gui option for more info. Examples: "x11vnc ... -gui" and
"x11vnc ... -gui other:0" in the latter case the gui is displayed on
other:0, not the X display x11vnc is polling.
Q-9: Can I make x11vnc more quiet and also go into the background
after starting up?
Use the [168]-q and [169]-bg options, respectively. (also: -quiet is
an alias for -q)
Note that under -bg the stderr messages will be lost unless you use
the "[170]-o logfile" option.
Q-10: Sometimes when a VNC viewer dies abruptly, x11vnc also dies with
the error message like: "Broken pipe". I'm using the -forever mode and
I want x11vnc to keep running.
As of Jan/2004 in the libvncserver CVS the SIGPIPE signal is ignored.
So if a viewer client terminates abruptly, libvncserver will notice on
the next I/O operation and will close the connection and continue on.
Up until of Apr/2004 the above fix only works for BSD signal systems
(Linux, FreeBSD, ...) For SYSV systems there is a workaround in my
[171]x11vnc.c file. It also has an [172]option -sigpipe exit to have
x11vnc clean up and exit upon receiving SIGPIPE.
Q-11: Are there any build-time customizations possible, e.g. change
defaults, create a smaller binary, etc?
As of Mar/2004 in the libvncserver cvs there are a few such options.
They are enabled by adding something like -Dxxxx=1 to the CPPFLAGS
environment variable before running configure (see the [173]build
notes for general background).
* -DX11VNC_SHARED=1 make -shared the default.
* -DX11VNC_FOREVER=1 make -forever the default.
* -DREMOTE_CONTROL=0 disable the remote control mechanism.
* -DSMALL_FOOTPRINT=1 strip out help text, gui, etc to make a
smaller binary (e.g. for PDA or embedded system with low disk
space). Also be sure to strip(1) the binary. Set to 2 or 3 to cut
out even more.
For example:
env CPPFLAGS="-DX11VNC_FOREVER=1" ./configure; make
If other things (e.g. "-I ...") are needed in CPPFLAGS add them as
well.
Be careful the the following two variables: HARDWIRE_PASSWD and
HARDWIRE_VIEWPASSWD. If set (remember to include the double quotes
around the string), they will be used as default values for the
-passwd and -viewpasswd options. Of course the strings will exist
unobscured in the x11vnc: the binary better not be readable by
unintendeds. Perhaps this is of use in remote access for an embedded
application, etc...
Let us know if more build-time customizations would be useful. Look
near the top of the source file for any additional customization
macros.
If the system does not have the XTEST XTestGrabControl interface (some
early X11R5 systems have XTEST but not this interface), then configure
will automatically try to see if the DEC-XTRAP extension build
environment is available and use that for avoiding GrabServer
deadlock. If you want DEC-XTRAP compiled in no matter what, set
X11VNC_USE_XTRAP=1 in your environment. Note that DEC-XTRAP should
only be used as a last resort on legacy machines since the standard
XTEST works well. If there is interest for legacy machines to use
DEC-XTRAP for all of the user input injection (not just grab control)
let us know and we will put it in for you to try. (Note: DEC-XTRAP
grab control seems to be broken on Linux/XFree86)
[Win2VNC Related]
Q-12: I have two separate machine displays in front of me, one Windows
the other X11: can I use x11vnc in combination with Win2VNC in
dual-screen mode to pass the keystrokes and mouse motions to the X11
display?
Yes, for best response start up x11vnc with the "[174]-nofb" option
(disables framebuffer polling, and does other optimizations) on the
secondary display (X11) machine. Then start up Win2VNC on the primary
display (Windows) referring it to the secondary display.
This will also work X11 to X11 using [175]x2vnc, however you would
probably just want to avoid VNC and use x2x for that.
For reference, here are some links to Win2VNC-like programs for
multiple monitor setups:
* [176]Original Win2VNC
* [177]Enhanced Win2VNC and [178]sourceforge link
* [179]x2vnc
* [180]x2x also [181]here
* [182]zvnc (MorphOS)
All of them will work with x11vnc (except x2x where it is not needed).
Q-13: I am running Win2VNC on my Windows machine and "x11vnc -nofb" on
Unix to pass keyboard and mouse to the Unix monitor. Whenever I start
Win2VNC it quickly disconnects and x11vnc says:
rfbProcessClientNormalMessage: read: Connection reset by peer
Is the default visual of the X display you run x11vnc on low color
(e.g. 8 bit per pixel PseudoColor)? (you can run xdpyinfo to check,
look in the "screen" section). There seems to be a bug in Win2VNC in
that it cannot deal correctly with colormaps (PseudoColor is the most
common example of a visual with a colormap).
If so, there are a couple options. 1) Can you set the default visual
on your display to be depth 24 TrueColor? Sun machines often have 8+24
overlay/multi-depth visuals, and you can make the default visual depth
24 TrueColor (see fbconfig(1) and Xsun(1)). 2) As of Feb/2004, in the
libvncserver CVS, x11vnc has the [183]-visual option to allow you to
force the framebuffer visual to whatever you want (this usually messes
up the colors unless you are very clever). In this case, the option
provides a convenient workaround for the Win2VNC bug:
x11vnc -nofb -visual TrueColor -display :0 ...
So the visual will be set to 8bpp TrueColor and Win2VNC can handle
this. Since Win2VNC does not use the framebuffer data there should be
no problems in doing this.
[Color Issues]
Q-14: The X display I run x11vnc on is only 8 bits per pixel (bpp)
PseudoColor (i.e. only 256 distinct colors). The x11vnc colors may
start out OK, but after a while they are incorrect in certain windows.
Use the [184]-flashcmap option to have x11vnc watch for changes in the
colormap, and propagate those changes back to connected clients. This
can be slow (since the whole screen must be updated over the network
whenever the colormap changes). This flashing colormap behavior often
happens if an application installs its own private colormap when the
mouse is in its window. "netscape -install" is a well-known historical
example of this. Consider reconfiguring the system to 16 bpp or depth
24 TrueColor if at all possible.
Also note that in some rare cases the [185]-notruecolor option has
corrected colors on 8bpp displays. The red, green, and blue masks were
non-zero in 8bpp PseudoColor on an obscure setup, and this option
corrected the problems.
Q-15: Color problems: Why are the colors for some windows messed up in
x11vnc? BTW, my X display has nice overlay/multi-depth visuals of
different color depths: e.g. there are both depth 8 and 24 visuals
available at the same time.
You may want to review the [186]previous question regarding 8 bpp
PseudoColor.
On some hardware (Sun/SPARC, Sgi), the [187]-overlay option discussed
a couple paragraphs down may solve this for you (you may want to skip
to it directly).
Run xdpyinfo(1) to see what the default visual is and what the depths
of the other visuals are. Does the default visual have a depth of 8?
If it does, can you possibly re-configure your X server to make the
depth 24 visual the default? If you can do it, this will save you a
lot of grief WRT colors and x11vnc (and for general usage too!). Here
is how I do this on an old Sparcstation 20 running Solaris 9 with SX
graphics
xinit -- -dev /dev/fb defclass TrueColor defdepth 24
and it works nicely (note: to log into console from the dtlogin
window, select "Options -> Command Line Login", then login and enter
the above command). See the -dev section of the Xsun(1) manpage for a
description of the above arguments. If you have root permission, a
more permanent and convenient thing to do is to record the arguments
in a line like:
:0 Local local_uid@console root /usr/openwin/bin/Xsun -dev /dev/fb defclass
TrueColor defdepth 24
in /etc/dt/config/Xservers (copy /usr/dt/config/Xservers). Also look
at the fbconfig(1) and related manpages (e.g. ffbconfig, m64config,
pgxconfig, SUNWjfb_config, etc ...) for hardware framebuffer settings
that may achieve the same effect.
In general for non-Sun machines, look at the "-cc class" and related
options in your X server manpage (perhaps Xserver(1)), it may allow
modifying the default visual (e.g. "-cc 4", see <X11/X.h> for the
visual class numbers). On XFree86 some video card drivers (e.g. Matrox
mga) have settings like Option "Overlay" "24,8" to support multi-depth
overlays. For these, use the "-cc 4" X server command line option to
get a depth 24 default visual.
The -overlay mode: Another option is if the system with overlay
visuals is a Sun system running Solaris or Sgi running IRIX you can
use the [188]-overlay x11vnc option (Aug/2004) to have x11vnc use the
Solaris XReadScreen(3X11) function to poll the "true view" of the
whole screen at depth 24 TrueColor. XReadDisplay(3X11) is used on
IRIX. This is useful for Legacy applications (older versions of
Cadence CAD apps are mentioned by x11vnc users) that require the
default depth be 8bpp, or the app will use a 8bpp visual even if depth
24 visuals are available, and so the default depth workaround
described in the previous paragraph is not sufficient for these apps.
Misc. notes on -overlay mode: An amusing by-product of -overlay mode
is that mouse cursor shape is correct. The -overlay mode may be
somewhat slower than normal mode due to the extra framebuffer
manipulations that must be performed. Also, on Solaris there is a bug
in that for some popup menus, the windows they overlap will have
painting errors (flashing colors) while the popup is up (a workaround
is to disable SaveUnders by passing -su to Xsun, e.g. in your
/etc/dt/config/Xservers file).
Colors still not working correctly? Run xwininfo on the application
with the messed up colors to verify that the depth of its visual is
different from the default visual depth (gotten from xdpyinfo). One
possible workaround in this case is to use the [189]-id option to
point x11vnc at the application window itself. If the application is
complicated (lots of toplevel windows and popup menus) this may not be
acceptable, and may even crash x11vnc (but not the application).
It is theoretically possible to solve this problem in general (see
xwd(1) for example), but it does not seem trivial or sufficiently fast
for x11vnc to be able to do so in real time. Fortunately the
[190]-overlay option works for Solaris machines with overlay visuals
where most of this problem occurs.
Q-16: How do I figure out the window id to supply to the -id windowid
option?
Run the xwininfo program in a terminal. It will ask you to click on
the desired application window. After clicking, it will print out much
information, including the window id (e.g. 0x6000010). Also, the
visual and depth of the window printed out is often useful in
debugging x11vnc [191]problems.
When using -id windowid, note that some VNC viewers will have problems
rendering screens that have a width that is not a multiple of 4. Try
to manually adjust the window width before starting x11vnc -id ....
Also, as of Dec/2004 libvncserver CVS you can use "[192]-id pick" to
have x11vnc run xwininfo(1) for you and after you click the window it
extracts the windowid. Besides "pick" there is also "id:root" to allow
you to go back to root window when doing remote-control.
Q-17: Why don't menus or other transient windows come up when I am
using the -id windowid option to view a single application window?
This is related to the behavior of the XGetImage(3X11) and
XShmGetImage() interfaces regarding backingstore, saveunders, etc. The
way the image is retrieved depends on some aspects of how the X server
maintains the display image data and whether other windows are
clipping or obscuring it. See the XGetImage man page for more details.
If you disable BackingStore and SaveUnders in the X server you should
be able to see these transient windows.
If things are not working and you still want to do the single window
polling, try the [193]-sid windowid option ("shifted" windowid).
x11vnc is known to crash under both -id and -sid, so both modes are
still experimental. Please report any reproducible bugs.
Q-18: My X display is depth 24 at 24bpp (instead of the normal depth
24 at 32bpp). I'm having lots of color and visual problems with x11vnc
and/or vncviewer. What's up?
First off, depth 24 at 24bpp (bpp=bits-per-pixel) is fairly uncommon
and can cause problems in general. It also can be slower than depth 24
at 32bpp. You might want to switch to 32bpp (for XFree86 see the
"-fbbpp 32", DefaultFbBpp, FbBpp and related options). Perhaps you
have 24bpp because the video memory of the machine is low and the
screen wouldn't fit in video RAM at 32bpp. For this case depth 16 at
16bpp might be an acceptable option.
In any event x11vnc should handle depth 24 at 24bpp (although
performance may be slower). There are some caveats involving the
viewer however:
The RealVNC Unix viewer cannot handle 24bpp from the server, it will
say: "main: setPF: not 8, 16 or 32 bpp?" and exit. I have not checked
the RealVNC Windows viewer.
So you need to use the TightVNC Unix viewer. However there are some
problems with that too. It seems libvncserver does not do 24bpp
correctly with the Tight encoding. The colors and screen ultimately
get messed up. So you have to use a different encoding with the
TightVNC vncviewer, try "zlib", "hextile", or one of the other
encodings (e.g. vncviewer -encodings "zlib hextile" ...). I have not
checked the TightVNC or UltraVNC Windows viewers.
It appears the older RealVNC Unix viewers (e.g. 3.3.3 and 3.3.7) can
handle 24bpp from the server, so you may want to use those. They
evidently request 32 bpp and libvncserver obliges.
Now coming the opposite direction if you are running the vncviewer on
the 24bpp display, TightVNC will fail with "Can't cope with 24
bits-per-pixel. Sorry." and RealVNC will fail with "main: Error:
couldn't find suitable pixmap format" so evidently you cannot use
24bpp for the vncviewers to work on that X display.
[Xterminals]
Q-19: Can I use x11vnc to view and interact with an Xterminal (e.g.
NCD) that is not running UNIX and so x11vnc cannot be run on it
directly?
You can, but it will likely be very wasteful of network bandwidth
since you will be polling the X display over the network as opposed to
over the local hardware. To do this, run x11vnc on a UNIX machine as
close as possible network-wise (e.g. same switch) to the Xterminal
machine. Use the [194]-display option to point the display to that of
the Xterminal (you'll of course need basic X11 permission to do that)
and also supply the [195]-noshm option (this enables the polling over
the network).
The response will likely be sluggish (maybe only one "frame" per
second). This mode is not recommended except for "quick checks" of
hard to get to X servers. Use something like -wait 150 to cut down on
the polling rate. You may also need [196]-flipbyteorder if the colors
get messed up due to endian byte order differences.
Q-20: How do I get my X permissions (MIT-MAGIC-COOKIE) correct for a
Unix/Linux machine acting as an Xterminal?
If the X display machine is a traditional Xterminal (where the X
server process runs on the Xterminal box, but all of the X client
applications (mozilla, etc) run on a central server (aka "terminal
server")), you will need to log into the Xterminal machine (i.e. get a
shell running there) and then start the x11vnc program. If the
Xterminal Linux/Unix machine is stripped down (e.g. no users besides
root) that may be difficult.
The next problem is the login Display Manager (e.g. gdm, kdm), and
hence the MIT-MAGIC-COOKIE auth files, are on the central server and
not on the Xterminal box where the X server and x11vnc processes are.
So unless X permissions are completely turned off (e.g. "xhost +"), to
run the x11vnc process on the Xterminal box the MIT-MAGIC-COOKIE auth
file data (XAUTHORITY or $HOME/.Xauthority) must be accessible by or
copied to the Xterminal. If $HOME/.Xauthority is exported via NFS
(this is insecure of course, but has been going on for decades), then
x11vnc can simply pick it up via NFS (you may need to use the
[197]-auth option to point to the correct file). Other options include
copying the auth file using scp, or something like:
central-server> xauth nextract - xterm123:0 | ssh xterm123 xauth nmerge -
and then, say, ssh from central-server to xterm123 to start x11vnc.
Here "xterm123" refers to the computer acting as the Xterminal and
"central-server" is the terminal server. You can use "xauth -f
/path/to/cookie-file list" to examine the contents of the cookie(s) in
a file "/path/to/cookie-file". See the xauth(1) manpage for more
details.
If the display name in the cookie file needs to be changed between the
two hosts, see [198]this note on the "xauth add ..." command.
A less secure option is to run something like "xhost +127.0.0.1" while
sitting at the Xterminal box to allow cookie-free local access for
x11vnc. You can run "xhost -127.0.0.1" after x11vnc connects if you
want to go back to the original permissions.
If the Xterminal is really stripped down and doesn't have any user
accounts, NFS, etc. you'll need to contact your system administrator
to set something up. It can be done!!! Some Xterminal projects have
actually enabled "run locally" facilities for the running of an
occasional app more efficiently locally on the Xterminal box (e.g.
realplayer).
Not recommended, but as a last resort, you could have x11vnc [199]poll
the Xterminal Display over the network. For this you would run a
"x11vnc -noshm ..." process on the central-server (and hope the
network admin doesn't get angry...)
Note: use of Display Manager (gdm, kdm, ...) auth cookie files (i.e.
from /var/..., /tmp/..., or elsewhere) may require modification via
xauth(1) to correctly include the display x11vnc refers to (e.g.
"xauth -f cookie-file add :0 . 45be51ae2ce9dfbacd882ab3ef8e96b1",
where the "45be51..." cookie value was found from an "xauth -f
/path/to/original/cookie-file list") or other reasons. See xauth(1)
manpage for full details on how to transfer an MIT-MAGIC-COOKIE
between machines and displays.
VNCviewer performance on Xterminals: This isn't related to x11vnc on
Xterminals, but we mention it here anyway because of the similar
issues. If you are on an Xterminal and want to use vncviewer to
connect to a VNC server somewhere, then performance would be best if
you ran the viewer on the Xterminal box. Otherwise, (i.e. running the
viewer process on the central-server) all of the vncviewer screen
drawing is done more inefficiently over the network. Something to
consider, especially on a busy network. (BTW, this has all of the
above permission, etc, problems: both vncviewer and x11vnc are X
client apps desired to be run on the Xterminal box).
[Remote Control]
Q-21: How do I stop x11vnc once it is running in the background?
As of Dec/2004 in the libvncserver CVS there is a remote control
feature. It can change a huge amount of things on the fly: see the
[200]-remote and [201]-query options. To shut down the running x11vnc
server just type "x11vnc -R stop". To disconnect all clients do
"x11vnc -R disconnect:all", etc.
For older versions: If the [202]-forever option has not been supplied,
x11vnc will automatically exit after the first client disconnects. In
general you will have to kill the x11vnc process This can be done via:
"kill NNNNN" (where NNNNN is the x11vnc process id number found from
ps(1)), or "pkill x11vnc", or "killall x11vnc" (Linux only).
If you have not put x11vnc in the background via the [203]-bg option
or shell & operator, then simply press Ctrl-C in the shell where
x11vnc is running to stop it. Potential Gotcha: If somehow your
Keypress of Ctrl-C went through x11vnc to the Xserver that then
delivered it to x11vnc it is possible one or both of the Ctrl or C
keys will be left stuck in the pressed down state in the Xserver.
Tapping the stuck key (either via a new x11vnc or at the physical
console) will release it from the stuck state. If the keyboard seems
to be acting strangely it is often fixed by tapping Ctrl, Shift, and
Alt. Alternatively, the [204]-clear_mods option and [205]-clear_keys
option can be used to release pressed keys at startup and exit.
Q-22: Can I change settings in x11vnc without having to restart it?
Can I remote control it?
Look at the [206]-remote (same as -R) and [207]-query (same as -Q)
options added in the Dec/2004 libvncserver CVS. They allow nearly
everything to be changed dynamically and settings to be queried.
Examples: "x11vnc -R shared", "x11vnc -R forever", "x11vnc -R
scale:3/4", "x11vnc -Q modtweak", "x11vnc -R stop", "x11vnc -R
disconnect:all", etc.. These commands do not start a x11vnc server,
but rather communicate with one that is already running. The X display
(VNC_CONNECT property) is used as the communication channel, so the X
permissions and DISPLAY must be set up correctly for communication to
be possible.
There is also a simple tcl/tk gui based on this remote control
mechanism. See the [208]-gui option for more info.
[Security and Permissions]
Q-23: How do I create a VNC password for use with x11vnc?
You may already have one in $HOME/.vnc/passwd if you have used, say,
the vncserver program from the regular RealVNC or TightVNC packages
(i.e. launching the Xvnc server). Otherwise, you could use the
vncpasswd(1) program from those packages. The libvncserver package
also comes with a simple program: storepasswd in the examples
directory. And as of Jun/2004 in the libvncserver CVS x11vnc supports
the -storepasswd "pass" "file" [209]option, which is the the same
functionality of storepasswd. Be sure to quote the "pass" if it
contains shell meta characters, spaces, etc. Example:
x11vnc -storepasswd 'sword*fish' $HOME/myvncpasswd
You then use the password via the x11vnc option: [210]-rfbauth
$HOME/myvncpasswd
Compared to vncpasswd(1) the latter two methods are a somewhat unsafe
because the password is specified on the command line and so someone
may see it by using ps(1) or looking over your shoulder. Also watch
out for the command winding up in your shell's history file (history
-c is often a way to clear it).
x11vnc also has the [211]-passwdfile and -passwd/-viewpasswd plain
text (i.e. not obscured like the -rfbauth VNC passwords) password
options.
Q-24: Can I have two passwords for VNC viewers, one for full access
and the other for view-only access to the display?
Yes, as of May/2004 in the libvncserver CVS there is the
[212]-viewpasswd option to supply the view-only password. Note the
full-access password option [213]-passwd must be supplied at the same
time. E.g.: -passwd sword -viewpasswd fish.
To avoid specifying the passwords on the command line (where they
could be observed via the ps(1) command by any user) you can use the
[214]-passwdfile option to specify a file containing plain text
passwords. Presumably this file is readable only by you, and ideally
it is located on the machine x11vnc is run on (to avoid being snooped
on over the network). The first line of this file is the full-access
password. If there is a second line in the file and it is non-blank,
it is taken as the view-only password. (use "__EMPTY__" to supply an
empty one).
View-only passwords currently do not work for the [215]-rfbauth
password option (standard VNC password storing mechanism). FWIW, note
that although the output (usually placed in $HOME/.vnc/passwd) by the
vncpasswd or storepasswd programs (or from x11vnc -storepasswd) looks
encrypted they are really just obscured to avoid "casual" password
stealing. It takes almost no skill to figure out how to extract the
plain text passwords from $HOME/.vnc/passwd since it is very
straight-forward to work out what to do from the VNC source code.
Q-25: Can I fine tune what types of user input are allowed? E.g. have
some users just be able to move the mouse, but not click or type
anything?
As of Feb/2005, the [216]-input option allows you to do this. "K",
"M", and "B" stand for Keystroke, Mouse-motion, and Button-clicks,
respectively. The setting: "-input M" makes attached viewers only able
to move the mouse. "-input KMB,M" lets normal clients do everything
and enables view-only clients to move the mouse.
These settings can also be applied on a per-viewer basis via the
remote control mechanism or the GUI. E.g. x11vnc -R input:hostname:M
Q-26: Why does x11vnc exit as soon as the VNC viewer disconnects? And
why doesn't it allow more than one VNC viewer to connect at the same
time?
These defaults are simple safety measures to avoid someone unknowingly
leaving his X11 desktop exposed (to the internet, say) for long
periods of time. Use the [217]-forever option (aka -many) to have
x11vnc wait for more connections after the first client disconnects.
Use the [218]-shared option to have x11vnc allow multiple clients to
connect simultaneously.
Recommended additional safety measures include using ssh ([219]see
above), stunnel, or a VPN to authenticate and encrypt the viewer
connections or to at least use the -rfbauth passwd-file [220]option to
use VNC password protection (or [221]-passwdfile) It is up to you to
apply these security measures, they will not be done for you
automatically.
Q-27: Can I limit which machines incoming VNC clients can connect
from?
Yes, look at the [222]-allow and [223]-localhost options to limit
connections by hostname or IP address. E.g.
x11vnc -allow 192.168.0.1,192.168.0.2
for those two hosts or
x11vnc -allow 192.168.0.
for a subnet. For individual hosts you can use the hostname instead of
the IP number, e.g.: "-allow snoopy", and "-allow darkstar,wombat".
Note that -localhost is the same as "-allow 127.0.0.1"
For more control, build libvncserver with libwrap support
[224](tcp_wrappers) and then use /etc/hosts.allow See hosts_access(5)
for complete details.
Q-28: How do I build x11vnc/libvncserver with libwrap (tcp_wrappers)
support?
Here is one way to pass this information to the configure script:
env CPPFLAGS=-DUSE_LIBWRAP LDFLAGS=-lwrap ./configure
then run make as usual. This requires libwrap and its development
package (tcpd.h) to be installed on the build machine. If additional
CPPFLAGS or LDFLAGS options are needed supply them as well using
quotes.
The resulting x11vnc then uses libwrap/tcp_wrappers for connections.
The service name you will use in /etc/hosts.allow and /etc/hosts.deny
is "vnc", e.g.:
vnc: 192.168.100.3 .example.com
Note that if you run x11vnc out of [225]inetd you do not need to build
x11vnc with libwrap support because the /usr/sbin/tcpd reference in
/etc/inetd.conf handles the tcp_wrappers stuff.
Q-29: Can I have x11vnc only listen on one network interface (e.g.
internal LAN) rather than having it listen on all network interfaces
and relying on -allow to filter unwanted connections out?
As of Mar/2005 in the libvncserver CVS, there is the "[226]-listen
ipaddr" option that enables this. For ipaddr either supply the desired
network interface's IP address (or use a hostname that resolves to it)
or use the string "localhost". For additional filtering simultaneously
use the "[227]-allow host1,..." option to allow only specific hosts
in.
This option is useful if you want insure that no one can even begin a
dialog with x11vnc from untrusted network interfaces (e.g. ppp0). The
option [228]-localhost now implies "-listen localhost" since that is
what most people expect it to do.
Q-30: Now that -localhost implies listening only on the loopback
interface, how I can occasionally allow in a non-localhost via the
allowonce remote control command?
To do this specify "[229]-allow localhost". Unlike [230]-localhost
this will leave x11vnc listening on all interfaces (but of course only
allowing in local connections, e.g. ssh redirs). Then you can later
run "x11vnc -R allowonce:somehost" or use to gui to permit a one-shot
connection from a remote host.
Note that if you do a lot of changing of the listening interface
([231]-listen option) via remote control or gui, you may need to also
manually adjust the [232]-allow list if you unexpectedly get into a
state where the allow list cannot match any hosts that would be coming
in on the listening interface. If you just toggle [233]-localhost on
and off x11vnc should see to it that you never get into such a state.
Q-31: How can I tunnel my connection to x11vnc via an encrypted SSH
channel between two Unix machines?
See the description earlier on this page on [234]how to tunnel VNC via
SSH from Unix to Unix. A number of ways are described along with some
issues you may encounter.
Other secure encrypted methods exists, e.g. stunnel, IPSEC, various
VPNs, etc.
Q-32: How can I tunnel my connection to x11vnc via an encrypted SSH
channel from Windows using an SSH client like Putty?
[235]Above we described how to tunnel VNC via SSH from Unix to Unix,
you may want to review it. To do this from Windows using Putty it
would go something like this:
* In the Putty dialog window under 'Session' enter the hostname or
IP number of the Unix machine with display to be viewed.
* Make sure the SSH protocol is selected and the server port is
correct.
* Under 'Connections/SSH/Tunnels' Add a Local connection with
'Source port: 5900' and 'Destination: localhost:5900'
* Log into the remote machine by pressing 'Open' and supplying
username, password, etc.
* In that SSH shell, start up x11vnc by typing the command: x11vnc
-display :0 plus any other desired options.
* Finally, start up your VNC Viewer in Windows and enter
'localhost:0' as the VNC server.
You can keep all of the settings in a Putty 'Saved Session'. Also,
once everything is working, you can consider putting x11vnc -display
:0 (plus other cmdline options) in the 'Remote command' Putty setting
under 'Connections/SSH'. It is likely possible to script the whole
process in a BAT file including launching the VNC viewer by using the
plink Putty utility. Send us the script if you get that working.
For extra protection feel free to run x11vnc with the [236]-localhost
and [237]-rfbauth/[238]-passwdfile options.
If the machine you SSH into via Putty is not the same machine with the
X display you wish to view (e.g. your company provides incoming SSH
access to a gateway machine), then you need to change the above Putty
dialog setting to: 'Destination: otherhost:5900', Once logged in,
you'll need to do a second login (ssh or rsh) to the workstation
machine 'otherhost' and then start up x11vnc on it.
As discussed [239]above another option is to first start the VNC
viewer in "listen" mode, and then launch x11vnc with the
"[240]-connect localhost" option to establish the reverse connection.
In this case a Remote port redirection (not Local) is needed for port
5500 instead of 5900 (i.e. 'Source port: 5500' and
'Destination: localhost:5500' for a Remote connection).
Q-33: Can I prompt the user at the local X display whether the
incoming VNC client should be accepted or not? Can I decide to make
some clients view-only? How about running an arbitrary program to make
the decisions?
Yes, look at the "[241]-accept command" option, it allows you to
specify an external command that is run for each new client. (use
quotes around the command if it contains spaces, etc.). If the
external command returns 0 the client is accepted, otherwise the
client is rejected. See below how to also accept clients view-only.
The external command will have the RFB_CLIENT_IP environment variable
set to the client's numerical IP address, RFB_CLIENT_PORT its port
number. Similarly for RFB_SERVER_IP and RFB_SERVER_PORT to allow
identification of the tcp virtual circuit. DISPLAY will be set to that
of the X11 display being polled. Also, RFB_X11VNC_PID is set to the
x11vnc process id (e.g. in case you decided to kill it), RFB_CLIENT_ID
will be an id number, and RFB_CLIENT_COUNT the number of other clients
currently connected. RFB_MODE will be "accept".
As a special case, "-accept popup" will instruct x11vnc to create its
own simple popup window. To accept the client press "y" or click mouse
on the "Yes" button. To reject the client press "n" or click mouse on
the "No" button. To accept the client View-only, press "v" or click
mouse on the "View" button. If the [242]-viewonly option has been
supplied, the "View" action will not be present: the whole display is
view only in that case.
The popup window times out after 120 seconds, to change this behavior
use "-accept popup:N" where N is the number of seconds (use 0 for no
timeout). More tricks: "-accept popupmouse" will only take mouse click
responses, while "-accept popupkey" will only take keystroke responses
(popup takes both). After any of the 3 popup keywords you can supply a
position of the window: +N+M, (the default is to center the window)
e.g. -accept popupmouse+10+10.
Also as a special case "-accept xmessage" will run the xmessage(1)
program to prompt the user whether the client should be accepted or
not. This requires that you have xmessage installed and available via
PATH. In case it is not already on your system, the xmessage program
is available at [243]ftp://ftp.x.org/
To include view-only decisions for the external commands, prefix the
command something like this: "yes:0,no:*,view:3 mycommand ..." This
associates the three actions: yes(accept), no(reject), and
view(accept-view-only), with the numerical return codes. Use "*"
instead of a number to set the default action (e.g. in case the
external command returns an unexpected return code).
Here is an example -accept script called accept_or_lock. It uses
xmessage and xlock (replace with your screen lock command, maybe it is
"xscreensaver-command -lock", or kdesktop_lock, or "dtaction
LockDisplay"). It will prompt the user at the X display whether to
accept, reject, or accept view-only the client, but if the prompt
times out after 60 seconds the screen is locked and the VNC client is
accepted. This allows the remote access when no one is at the display.
#!/bin/sh
#
# accept_or_lock: prompt user at X display whether to accept an incoming
# VNC connection. If timeout expires, screen is locked
# and the VNC viewer is accepted (allows remote access
# when no one is sitting at the display).
#
# usage: x11vnc ... -forever -accept 'yes:0,no:*,view:4 accept_or_lock'
#
xmessage -buttons yes:2,no:3,view-only:4 -center \
-timeout 60 "x11vnc: accept connection from $RFB_CLIENT_IP?"
rc=$?
if [ $rc = 0 ]; then
xlock &
sleep 5
exit 0
elif [ $rc = 2 ]; then
exit 0
elif [ $rc = 4 ]; then
exit 4
fi
exit 1
Stefan Radman has written a nice dtksh script [244]dtVncPopup for use
in CDE environments to do the same sort of thing. Information on how
to use it is found at the top of the file. He encourages you to
provide feedback to him to help improve the script.
Note that in all cases x11vnc will block while the external command or
popup is being run, so attached clients will not receive screen
updates, etc during this period.
To run a command when a client disconnects, use the "[245]-gone
command" option. This is for the user's convenience only: the return
code of the command is not interpreted by x11vnc. The same environment
variables are set as in "-accept command" (except that RFB_MODE will
be "gone").
Q-34: Does x11vnc support Unix usernames and passwords? Can I further
limit the set of Unix usernames who can connect to the VNC desktop?
Until the VNC protocol and libvncserver support this things will be
approximate at best. Hopefully, it will not be too long to wait for
such support.
One approximate method involves starting x11vnc with the
[246]-localhost option. This basically requires the viewer user to log
into the workstation where x11vnc is running via their Unix username
and password, and then somehow set up a port redirection of his
vncviewer connection to make it appear to emanate from the local
machine. As discussed above, ssh is useful for this: ssh -l username
-L 5900:localhost:5900 hostname ... See the ssh wrapper scripts
mentioned [247]elsewhere on this page. Of course a malicious user
could allow other users to get in through his channel, but that is a
problem with every method. Another thing to watch out for is a
malicious user on the viewer side (where ssh is running) trying to
sneak in through the ssh port redirection.
Regarding limiting the set of Unix usernames who can connect, the
traditional way would be to further require a VNC password to supplied
(-rfbauth, -passwd, etc). A scheme that avoids a second password
involves using the [248]-accept option that runs a program to examine
the connection information to determine which user is connecting from
the local machine. For example, the program could use the ident
service on the local machine (normally ident should not be trusted
over the network, but on the local machine it should be accurate:
otherwise root has been compromised and so there are more serious
problems!). An example script passed in via -accept scriptname that
deduces the Unix username and limits who can be accepted might look
something like this:
#!/bin/sh
if [ "$RFB_CLIENT_IP" != "127.0.0.1" -o "$RFB_SERVER_IP" != "127.0.0.1" ]; then
exit 1 # something fishy... reject it.
fi
user=`echo "$RFB_CLIENT_PORT, $RFB_SERVER_PORT" | nc -w 1 $RFB_CLIENT_IP 113 \
| grep 'USERID.*UNIX' | head -1 | sed -e 's/[\r ]//g' | awk -F: '{print
$4}'`
for okuser in fred barney wilma betty
do
if [ "X$user" = "X$okuser" ]; then
exit 0 # accept it
fi
done
exit 1 # reject it
For this to work with ssh port redirection, the ssh option
UsePrivilegeSeparation must be enabled.
Q-35: I start x11vnc as root because it is launched via inetd(1) or a
display manager like gdm(1). Can I have x11vnc later switch to a
different user?
As of Feb/2005 x11vnc has the [249]-users option that allows things
like this. Please read the documentation on it (in the x11vnc -help
output) carefully for features and caveats. It's use can often
decrease security unless care is taken. A nice use of it is "-users
+nobody" that switches to the Unix user nobody right after connections
to the X display are established.
Q-36: I use a screen-lock when I leave my workstation (e.g.
xscreensaver or xlock). When I remotely access my workstation desktop
via x11vnc I can unlock the desktop fine, but I am worried people will
see my activities on the physical monitor. What can I do to prevent
this, or at least make it more difficult?
Probably most work environments would respect your privacy if you
powered off the monitor. Also remember if people have physical access
to your workstation they basically can do anything they want with it
(e.g. install a backdoor for later use, etc).
In any event, as of Jun/2004 there is an experimental utility to make
it more difficult for nosey people to see your x11vnc activities. The
source for it is [250]blockdpy.c The idea behind it is simple (but
obviously not bulletproof): when a VNC client attaches to x11vnc put
the display monitor in the DPMS "off" state, if the DPMS state ever
changes immediately start up the screen-lock program. The x11vnc user
will notice something is happening and think about what to do next
(while the screen is in a locked state).
This works (or at least has a chance of working) because if the
intruder moves the mouse or presses a key on the keyboard, the monitor
wakes up out of the DPMS off state, and this induces the screen lock
program to activate as soon as possible. Of course there are cracks in
this, the eavesdropper could detach your monitor and insert a non-DPMS
one, and there are race conditions. As mentioned above this is not
bulletproof. A really robust solution would likely require X server
and perhaps even video hardware support.
The blockdpy utility is launched by the [251]-accept option and told
to exit via the [252]-gone option (the vnc client user should
obviously re-lock the screen before disconnecting!). Instructions can
be found in the source code for the utility at the above link.
Q-37: Can I have x11vnc automatically lock the screen when I
disconnect the VNC viewer?
Yes, a user mentions he uses the [253]-gone option under CDE to run a
screen lock program:
x11vnc -display :0 -forever -gone 'dtaction LockDisplay'
Other possibilities are:
x11vnc -display :0 -forever -gone 'xscreensaver-command -lock'
x11vnc -display :0 -forever -gone 'kdesktop_lock'
x11vnc -display :0 -forever -gone 'xlock &'
[Display Managers and Services]
Q-38: How can I run x11vnc as a "service" that is always available?
There are a number of ways to do this. The primary thing you need to
decide is whether you want x11vnc to connect to the X session on the
machine 1) regardless of who (or if anyone) has the X session, or 2)
only if a certain user has the X session. Because X sessions are
protected by X permissions (XAUTHORITY and $HOME/.Xauthority) the
automatically started x11vnc will of course need to have sufficient
permissions to connect to the X display.
Here are some ideas:
* Use the description under "Continuously" in the [254]FAQ on x11vnc
and Display Managers
* Use the description in the [255]FAQ on x11vnc and inetd(1)
* Start x11vnc from your $HOME/.xsession (or $HOME/.xinitrc)
* Although less reliable, see the [256]x11vnc_loop rc.local hack
below.
The display manager scheme will not be specific to which user has the
X session unless a test is specifically put into the display startup
script (often named Xsetup). The inetd(1) scheme may or may not be
specific to which user has the X session (and it may not be able to do
all users via the XAUTHORITY permission issues).
The $HOME/.xsession scheme is obviously is specific to a particular
user. If you do not know what a $HOME/.xsession script is or how to
use one, perhaps your desktop has a "session startup commands"
configuration option. The command to be run in the .xsession or
.xinitrc file may look like this:
x11vnc -logfile $HOME/.x11vnc.log -rfbauth $HOME/.vnc/passwd -forever -bg
plus any other options you desire.
Q-39: How can I use x11vnc to connect to an X login screen like xdm,
GNOME gdm, KDE kdm, or CDE dtlogin? (i.e. nobody is logged into an X
session yet).
One time only. If the X login screen is running and you just want to
connect to it once (i.e. a one-shot):
It is usually possible to do this by just adjusting the XAUTHORITY
environment variable to point to the correct MIT-COOKIE auth file
while running x11vnc as root, e.g. for the gnome display manager, gdm:
x11vnc -auth /var/gdm/:0.Xauth -display :0
(the [257]-auth option sets the XAUTHORITY variable for you).
There will be a similar thing for xdm using however a different auth
directory path (perhaps something like
/var/lib/xdm/authdir/authfiles/A:0-XQvaJk for xdm or
/var/lib/kdm/A:0-crWk72 for kdm, where the random characters in
basename will vary a bit). Read your system docs to find out where the
display manager cookie files are kept.
Trick: sometimes ps(1) can reveal the X server process -auth argument
(e.g. "ps wwwwaux | grep auth").
You next connect to x11vnc with a VNC viewer, give your username and
password to the X login prompt to start your session.
Note: gdm seems to have an annoying setting that causes x11vnc (and
any other X clients) to be killed after the user logs in. Setting
KillInitClients=false in the [daemon] section of /etc/X11/gdm/gdm.conf
avoids this. Otherwise, just restart x11vnc and then reconnect your
viewer.
Note: For dtlogin in addition to the above sort of trick (BTW, the
auth file should be in /var/dt), you'll also need to add something
like Dtlogin*grabServer:False to the Xconfig file
(/etc/dt/config/Xconfig or /usr/dt/config/Xconfig on Solaris, see
[258]the example at the end of this FAQ). Then restart dtlogin, e.g.:
/etc/init.d/dtlogin stop; /etc/init.d/dtlogin start or reboot.
Continuously. Have x11vnc reattach each time the X server is
restarted (i.e. after each logout):
To make x11vnc always attached to the the X server (please consider
the security implications of this!) including the login screen you
will need to add a command to a display manager startup script. The
name of the script file depends on desktop used and seem to be:
GNOME /etc/X11/gdm/Init/Default (or Init/:0)
KDE /etc/kde*/kdm/Xsetup
XDM /etc/X11/xdm/Xsetup (or xdm/Xsetup_0)
CDE /etc/dt/config/Xsetup
although the exact location can depend on operating system and
distribution. See the documentation for your display manager: gdm(1),
kdm(1), xdm(1), dtlogin(1) for additional details. There may also be
display number specific scripts: e.g. Xsetup_0 vs. Xsetup, you need to
watch out for.
Note: The above gdm setting of KillInitClients=false in
/etc/X11/gdm/gdm.conf is needed here as well.
Note: The above Dtlogin*grabServer:False step will be needed for
dtlogin here as well.
In any event, the line you will add to the display manager script will
look something like:
/usr/local/bin/x11vnc -rfbauth /path/to/the/vnc/passwd -o /tmp/x11vnc.log -fo
rever -bg
where you should customize the exact command to your needs.
Happy, happy, joy, joy: Note that we do not need to specify -display
or -auth because happily they are already set for us in the DISPLAY
and XAUTHORITY environment variables for the Xsetup script!!!
You may also want to force the VNC port with something like "-rfbport
5900"
_________________________________________________________________
Fedora/gdm: Here is an example of what we did on a vanilla install of
Fedora-C3 (seems to use gdm by default). Add a line like this to
/etc/X11/gdm/Init/:0
/usr/local/bin/x11vnc -rfbauth /etc/x11vnc.passwd -forever -bg -o /tmp/x11vnc
.log
And then add this line to /etc/X11/gdm/gdm.conf in the [daemon]
section:
KillInitClients=false
Then restart: /usr/sbin/gdm-restart (or reboot). The
KillInitClients=false setting is important: without it x11vnc will be
killed immediately after the user logs in. Here are [259]full details
on how to configure gdm
_________________________________________________________________
Solaris/dtlogin: Here is an example of what we did on a vanilla
install of Solaris:
Make the directory /etc/dt/config:
mkdir -p /etc/dt/config
Copy over the Xconfig file for customization:
cp /usr/dt/config/Xconfig /etc/dt/config/Xconfig
Edit /etc/dt/config/Xconfig and uncomment the line:
Dtlogin*grabServer: False
Next, copy over Xsetup for customization:
cp /usr/dt/config/Xsetup /etc/dt/config/Xsetup
Edit /etc/dt/config/Xsetup and at the bottom put a line like:
/usr/local/bin/x11vnc -forever -o /var/tmp/x11vnc.log -bg
(tweaked to your local setup and preferences, a password via -rfbauth,
etc. would be a very good idea).
Restart the X server and dtlogin:
/etc/init.d/dtlogin stop
/etc/init.d/dtlogin start
(or reboot or maybe just restart the X session).
_________________________________________________________________
KDM: One user running the kdm display manager reports putting this
line:
x11vnc -forever -rfbauth /home/xyz/.vnc/passwd -bg -o /tmp/x11vnc.log
in /etc/kde/kdm/Xsetup. After rebooting the system it all seemed to
work fine.
_________________________________________________________________
If you do not want to deal with any display manager startup scripts,
here is a kludgey script that can be run manually or out of a boot
file like rc.local: [260]x11vnc_loop It will need some local
customization before running. Because the XAUTHORITY auth file must be
guessed by this script, use of the display manager script method
described above is greatly preferred.
If the machine is a traditional Xterminal you may want to read
[261]this FAQ.
Q-40: Can I run x11vnc out of inetd(1)? How about xinetd(1)?
Yes, perhaps a line something like this in /etc/inetd.conf will do it
for you:
5900 stream tcp nowait root /usr/sbin/tcpd /usr/local/bin/x11vnc_sh
where the shell script /usr/local/bin/x11vnc_sh uses the [262]-inetd
option and looks something like (you'll need to customize to your
settings).
#!/bin/sh
/usr/local/bin/x11vnc -inetd -display :0 -auth /home/fred/.Xauthority \
-rfbauth /home/fred/.vnc/passwd -o /tmp/x11vnc_sh.log
Important: Note that you must redirect the standard error output to a
log file (e.g. -o file) or to /dev/null for proper operation via inetd
(otherwise the standard error also goes to the VNC vncviewer, and that
confuses it greatly). If you do not use a wrapper script as above but
rather call x11vnc directly in /etc/inetd.conf and do not redirect
stderr to a file, then you must specify the -q (aka [263]-quiet)
option: "/usr/local/bin/x11vnc -q -inetd ..." or use "-o logfile" to
collect the output in a file. The wrapper script with redirection to a
log file is the recommended method because the errors and warnings
printed out are very useful in troubleshooting problems.
Note also the need to set XAUTHORITY via [264]-auth to point to the
MIT-COOKIE auth file to get permission to connect to the X display
(setting and exporting the XAUTHORITY variable accomplishes the same
thing). See the x11vnc_loop file in the previous question for more
ideas on what that auth file may be, etc.
Note: On Solaris you cannot have the bare number 5900 in
/etc/inetd.conf, you'll need to replace it with a word like x11vnc an
then put something like "x11vnc 5900/tcp" in /etc/services.
Be sure to look at your /etc/hosts.allow and /etc/hosts.deny settings
to limit the machines that can connect to this service (your
desktop!). For the above example with /etc/hosts.allow:
x11vnc_sh : 123.45.67.89
A really safe way to do things is to limit the above inetd to
localhost only (via /etc/hosts.allow) and use ssh to tunnel the
incoming connection. Using inetd for this prevents there being a tiny
window of opportunity between x11vnc starting up and your vncviewer
connecting to it. Always use a VNC password to further protect against
unwanted access.
For xinetd(1), one user reports he created the file
/etc/xinetd.d/x11vncservice containing the following:
# default: off
# description:
service x11vncservice
{
flags = REUSE NAMEINARGS
port = 5900
type = UNLISTED
socket_type = stream
protocol = tcp
wait = no
user = root
server = /usr/sbin/tcpd
server_args = /usr/local/bin/x11vnc_sh
disable = no
}
With the contents of /usr/local/bin/x11vnc_sh similar to the example
given above.
Q-41: How do I make x11vnc work with the Java VNC viewer applet in a
web browser?
To have x11vnc serve up a Java VNC viewer applet to any web browsers
that connect to it, run x11vnc with this [265]option:
-httpdir /path/to/the/java/classes/dir
(this directory will contain the files index.vnc and, for example,
VncViewer.jar) Note that libvncserver contains the TightVNC Java
classes jar file for your convenience. (it is the file
classes/VncViewer.jar in the source tree).
You will see output something like this:
14/05/2004 11:13:56 Autoprobing selected port 5900
14/05/2004 11:13:56 Listening for HTTP connections on TCP port 5800
14/05/2004 11:13:56 URL http://walnut:5800
14/05/2004 11:13:56 screen setup finished.
14/05/2004 11:13:56 The VNC desktop is walnut:0
PORT=5900
then you can connect to that URL with any Java enabled browser. Feel
free to customize the default index.vnc file in the classes directory.
Note that if you wanted to, you could also start the Java viewer
entirely from the viewer-side by having the jar file there and using
either the java or appletviewer commands to run the program.
Q-42: Are reverse connections (i.e. the VNC server connecting to the
VNC viewer) using "vncviewer -listen" and vncconnect(1) supported?
As of Mar/2004 in the libvncserver CVS x11vnc supports reverse
connections. On Unix one starts the VNC viewer in listen mode:
vncviewer -listen (see your documentation for Windows, etc), and then
starts up x11vnc with the [266]-connect option. To connect immediately
at x11vnc startup time use the "-connect host:port" option (use commas
for a list of hosts to connect to). The ":port" is optional (default
is 5500). If a file is specified instead: -connect /path/to/some/file
then that file is checked periodically (about once a second) for new
hosts to connect to.
To use the vncconnect(1) program (from the core VNC package at
www.realvnc.com) specify the [267]-vncconnect option to x11vnc (Note:
as of Dec/2004 -vncconnect is now the default). vncconnect(1) must be
pointed to the same X11 DISPLAY as x11vnc (since it uses X properties
to communicate with x11vnc). If you do not have or do not want to get
the vncconnect(1) program, the following script (named "Vncconnect")
may work if your xprop(1) supports the -set option:
#!/bin/sh
# usage: Vncconnect <host>
# Vncconnect <host:port>
# note: not all xprop(1) support -set.
#
xprop -root -f VNC_CONNECT 8s -set VNC_CONNECT "$1"
Q-43: Can I use x11vnc as a replacement for Xvnc? (i.e. not for a real
display, but for a virtual one I keep around).
You can, but you would not be doing this for performance reasons (for
virtual X sessions, Xvnc will give the fastest response). You may want
to do this because Xvnc does not support an X server extension you
desire, or you want to take advantage of one of x11vnc's unending
number of options and features.
One way to acheive this is to have a Xvfb(1) virtual framebuffer X
server running in the background and have x11vnc attached to it. One
could view this desktop both remotely and locally using vncviewer.
Make sure vncviewer's "-encodings raw" is in effect for local viewing
(compression seems to slow things down locally).
Here is one way to start up Xvfb:
xinit -- /usr/X11R6/bin/Xvfb :1 -screen 0 1024x768x16
This starts up a 16bpp virtual display. To export it via VNC use
"x11vnc -display :1 ...".
One good thing about Xvfb is that the virtual framebuffer exists in
main memory (rather than in the video hardware), and so x11vnc can
"screen scrape" it efficiently (more than, say, 100X faster than
normal video hardware).
There are some annoyances WRT Xvfb though. The default keyboard
mapping seems to be very poor. One should run x11vnc with
[268]-add_keysyms option to have keysyms added automatically. Also, to
add the Shift_R and Control_R modifiers something like this is needed:
#!/bin/sh
xmodmap -e "keycode any = Shift_R"
xmodmap -e "add Shift = Shift_L Shift_R"
xmodmap -e "keycode any = Control_R"
xmodmap -e "add Control = Control_L Control_R"
Perhaps the Xvfb options -xkbdb or -xkbmap could be used to get a
better default keyboard mapping.
One can use this sort of scheme to export other virtual X sessions,
say Xnest or even Xvnc itself (useful for testing x11vnc).
Q-44: How can I use x11vnc on "headless" machines? Why might I want
to?
An interesting application of x11vnc is to let it export displays of
"headless" machines. For example, you may have some lab or server
machines with no keyboard, mouse, or monitor, but each one still has a
video card. One can use x11vnc to provide a simple "desktop service"
from these server machines.
An X server can be started on the headless machine (sometimes this
requires configuring the X server to not fail if it cannot detect a
keyboard or mouse, see the next paragraph). Then you can export that X
display via x11vnc (e.g. see [269]this FAQ) and access it from
anywhere on the network via a VNC viewer.
Some tips on getting X servers to start on machines without keyboard
or mouse: For XFree86/Xorg the Option "AllowMouseOpenFail" "true"
"ServerFlags" config file option is useful. On Solaris Xsun the
+nkeyboard and +nmouse options are useful (put them in the server
command line args in /etc/dt/config/Xservers). See Xserver(1) for more
info.
Although this usage may sound strange it can be quite useful for a GUI
(or other) testing or QA setups: the engineers do not need to walk to
lab machines running different hardware, OS's, versions, etc (or have
many different machines in their office). They just connect to the
various test machines over the network via VNC. The advantage to
testing this way instead of using Xvnc or even Xvfb is that the test
is done using the real X server, fonts, video hardware, etc. that will
be used in the field.
One can imagine a single server machine crammed with as many video
cards as it can hold to provide multiple simultaneous access or
testing on different kinds of video hardware.
[Resource Usage and Performance]
Q-45: I have lots of memory, but why does x11vnc fail with shmget:
No space left on device or Minor opcode of failed request: 1
(X_ShmAttach)?
It is not a matter of free memory, but rather free shared memory (shm)
slots, also known as shm segments. This often occurs on a public
Solaris machine using the default of only 100 slots. You (or the owner
or root) can clean them out with ipcrm(1). x11vnc tries hard to
release its slots, but it, and other programs, are not always able to
(e.g. if kill -9'd).
Sometimes x11vnc will notice the problem with shm segments and tries
to get by with fewer, only giving a warning like this:
19/03/2004 10:10:58 shmat(tile_row) failed.
shmat: Too many open files
19/03/2004 10:10:58 error creating tile-row shm for len=4
19/03/2004 10:10:58 reverting to single_copytile mode
Here is a shell script [270]shm_clear to list and prompt for removal
of your unattached shm segments (attached ones are skipped). I use it
while debugging x11vnc (I use "shm_clear -y" to assume "yes" for each
prompt). If x11vnc is regularly not cleaning up its shm segments,
please contact me so we can work to improve the situation.
Longer term, on Solaris you can put something like this in
/etc/system:
set shmsys:shminfo_shmmax = 0x2000000
set shmsys:shminfo_shmmni = 0x1000
to sweep the problem under the rug (4096 slots). On Linux, examine
/proc/sys/kernel/shmmni; you can modify the value by writing to that
file.
Things are even more tight on Solaris 8 and earlier, there is a
default maximum number of shm segments per process of 6. The error is
the X server (not x11vnc) being unable to attach to the segments, and
looks something like this:
30/04/2004 14:04:26 Got connection from client 192.168.1.23
30/04/2004 14:04:26 other clients:
X Error of failed request: BadAccess (attempt to access private resource den
ied)
Major opcode of failed request: 131 (MIT-SHM)
Minor opcode of failed request: 1 (X_ShmAttach)
Serial number of failed request: 14
Current serial number in output stream: 17
This tight limit on Solaris 8 can be increased via:
set shmsys:shminfo_shmseg = 100
in /etc/system. See the next paragraph for more workarounds.
To minimize the number of shm segments used by x11vnc try using the
[271]-onetile option (corresponds to only 3 shm segments used, and
adding -fs 1.0 knocks it down to 2). If you are having much trouble
with shm segments, consider disabling shm completely via the
[272]-noshm option. Performance will be somewhat degraded but when
done over local machine sockets it should be acceptable (see an
[273]earlier question discussing -noshm).
Q-46: How can I make x11vnc use less system resources?
The [274]-nap and "[275]-wait n" (where n is the sleep between polls
in milliseconds, the default is 30 or so) option are good places to
start. Reducing the X server bits per pixel depth (e.g. to 16bpp or
even 8bpp) will further decrease memory I/O and network I/O. Using the
[276]-onetile option will use less memory and use fewer shared memory
slots (add [277]-fs 1.0 for one less slot).
Q-47: How can I make x11vnc use MORE system resources?
You can try [278]-threads and dial down the wait time (e.g. -wait 1)
and possibly dial down [279]-defer as well. Note that if you try to
increase the "frame rate" too much you can bog down the server end
with the extra work it needs to do compressing the framebuffer data,
etc.
That said, it is possible to "stream" video via x11vnc if the video
window is small enough. E.g. a 256x192 xawtv TV capture window (using
the x11vnc [280]-id option) can be streamed over a LAN or wireless at
a reasonable frame rate.
Q-48: I use x11vnc over a slow link with high latency (e.g. dialup
modem), is there anything I can do to speed things up?
Some things you might want to experiment with (most of which will help
performance on faster links as well):
X server/session parameters:
* Configure the X server bits per pixel to 16bpp or even 8bpp.
(reduces amount of data needed to be sent)
* Use a smaller desktop size (e.g. 1024x768 instead of 1280x1024)
* Make sure the desktop background is a solid color (the background
is resent every time it is re-exposed). Consider using the
[281]-solid [color] option.
* Configure your window manager or desktop "theme" to not use fancy
images, shading, and gradients for the window decorations, etc.
Disable Opaque moves, resizes, and animations.
* Avoid small scrolls of large windows using the Arrow keys or
scrollbar. Try to use PageUp/PageDown instead.
* Turn off Anti-aliased fonts on your system, web browser,
terminals, etc. AA fonts do not compress as well as traditional
fonts.
* On XFree86 turn on the Shadow Framebuffer to speed up reading.
(Option "ShadowFB" "true", and possibly Option "NoAccel" "true" as
well, in the Device section of /etc/X11/XF86Config) This disables
2D acceleration on the physical display and so is probably not
worth it, but could be of use in some situations.
VNC viewer parameters:
* Use a [282]TightVNC enabled viewer!
* Make sure the tight encoding is being used (look at vncviewer and
x11vnc outputs)
* Request 8 bits per pixel using -bgr233 (up to 4X speedup over
depth 24 TrueColor (32bpp), but colors will be off)
* The -depth option is similar to -bgr233 in reducing the requested
number of bits per pixel.
* Try increasing the TightVNC -compresslevel (compresses more on
server side before sending, but uses more CPU)
* Try reducing the TightVNC -quality (increases JPEG compression,
but is lossy)
* Try other VNC encodings via -encodings (tight is probably fastest,
but you should check)
* On the machine where vncviewer is run, make sure Backing Store is
enabled (XFree86 disables it by default causing re-exposures of
vncviewer to be very slow)
x11vnc parameters:
* Try using [283]-nodragging (no screen updates when dragging mouse,
but sometimes you miss visual feedback)
* Try the [284]-progressive pixelheight mode with the block
pixelheight 100 or so (delays sending vertical blocks since they
may change while viewer is receiving earlier ones)
* Set [285]-fs 1.0 (disables fullscreen updates)
* Try increasing [286]-wait or [287]-defer (reduces the maximum
"frame rate", but won't help much for large screen changes)
* If you just want to watch one (simple) window use [288]-id (cuts
down extraneous polling and updates, but can be buggy or
insufficient)
* Set [289]-nosel (disables all clipboard selection exchange)
* Use [290]-nocursor and [291]-nocursorpos (repainting the remote
cursor position and shape takes resources and round trips)
Q-49: When I drag windows around with the mouse or scroll up and down
things really bog down (unless I do the drag in a single, quick
motion). Is there anything to do to improve things?
This problem is primarily due to slow read rates from video cards: as
you scroll or move a large window around the screen changes are much
too rapid for x11vnc to keep up them (it can usually only read the
video card at about 5 MB/sec, so it can take a good fraction of a
second to read the changes induce from moving a large window, if this
to be done a number of times in succession the window or scroll
appears to "lurch" forward). See the description in the
[292]-pointer_mode option for more info. The next bottleneck is
compressing all of these changes and sending them out to connected
viewers, however the VNC protocol is pretty much self-adapting with
respect to that (updates are only packaged and sent when viewers ask
for them).
As of Jan/2004 there are some improvements in the libvncserver CVS
tree. The default should now be much better than before and dragging
small windows around should no longer be a huge pain. If for some
reason these changes make matters worse, you can go back to the old
way via the "[293]-pointer_mode 1" option.
Also added was the [294]-nodragging option that disables all screen
updates while dragging with the mouse (i.e. mouse motion with a button
held down). This gives the snappiest response, but might be undesired
in some circumstances when you want to see the visual feedback while
dragging (e.g. menu traversal or text selection).
As of Dec/2004 in the libvncserver CVS the [295]-pointer_mode n option
was introduced. n=1 is the original mode, n=2 an improvement, etc..
See the -pointer_mode n help for more info.
Also, in some circumstances the [296]-threads option can improve
response considerably. Be forewarned that if more than one vncviewer
is connected at the same time then libvncserver may not be thread safe
(try to get the viewers to use different VNC encodings, e.g. tight and
ZRLE).
See the [297]wireframe FAQ below for a scheme to sweep this problem
under the rug for window moves or resizes.
Q-50: Why not do something like wireframe animations to avoid the
windows "lurching" when being moved or resized?
Nice idea for a hack! As of Apr/2005 in the libvncserver CVS x11vnc by
default will apply heuristics to try to guess if a window is being
(opaquely) moved or resized. If such a change is detected framebuffer
polling and updates will be suspended and only an animated "wireframe"
(a rectangle outline drawn where the moved/resized window would be) is
shown. When the window move/resize stops, it returns to normal
processing: you should only see the window appear in the new position.
This spares you from interacting with a "lurching" window between all
of the intermediate steps. BTW the lurching is due to [298]slow video
card read rates. A displacement, even a small one, of a large window
requires a non-negligible amount of time, a good fraction of a second,
to read in from the hardware framebuffer.
The mode is currently on by default because most people are inflicted
with the problem. It can be disabled with the [299]-nowireframe
option. Why might one want to turn off the wireframing? Since x11vnc
is merely guessing when windows are being moved/resized, it may guess
poorly for your window-manager or desktop, or even for the way you
move the pointer. If your window-manager or desktop already does its
own wireframing then this mode is a waste of time and could do the
wrong thing occasionally. There may be other reasons the new mode
feels unnatural. If you have very expensive video hardware (SGI) or
are using an in-RAM video framebuffer (SunRay, ShadowFB, Xvfb), the
read rate from that framebuffer may be very fast (100's of MB/sec) and
so you don't really see much lurching: opaque moves look smooth in
x11vnc. Note: ShadowFB is often turned on when you are using the
vesafb or fbdev XFree86 video driver instead of a native one.
The heuristics used to guess window motion or resizing are simple, but
are not fool proof: x11vnc is sometimes tricked and so you'll
occasionally see the lurching opaque move and rarely something even
worse. First it assumes that the move/resize will occur with a mouse
button pressed, held down and dragged (of course this is only mostly
true). Next it will only consider a window for wireframing if the
mouse pointer is initially "close enough" to the edges of the window
frame, e.g. you have grabbed the title bar or a resizer edge (this
requirement can be disabled). If these are true, it will wait an
amount of time to see if the window starts moving or resizing. If it
does, it starts drawing the wireframe "outline" of where the window
would be. When the mouse button is released, or a timeout occurs, it
goes back to the standard mode to allow the actual framebuffer changes
to propagate to the viewers.
These parameters can be tweaked:
* Color/Shade of the wireframe.
* Linewidth of the outline frame.
* Cutoff size of windows to not apply wireframing to.
* Cutoffs for closeness to Top, Bottom, Left, and Right edges of
window.
* Maximum time to wait for dragging pointer events.
* Maximum time to wait for the window to start moving/resizing.
* Maximum time to show a wireframe animation.
* Minimum time between sending wireframe outlines.
See the [300]"-wireframe tweaks" option for more details. On a slow
link, e.g. dialup modem, you may want to increase all four of these
times, e.g. double them from the defaults.
CopyRect encoding: In addition to the above there is the
[301]"-wirecopyrect mode" option. It is also on by default. This
instructs x11vnc to not only show show the wireframe animation, but to
also instruct all connected VNC viewers to locally translate the
window image data from the original position to the new position on
the screen when the animation is done. This speedup is the VNC
CopyRect encoding: the framebuffer update doesn't need to send the
actual new image data. This is nice in general, and very convenient
over a slow link, but since it is based on heuristics you may need to
disable it with the -nowirecopyrect option if it works incorrectly or
unnaturally for you.
The -wirecopyrect modes are: "never" (same as -nowirecopyrect); "top",
only apply the CopyRect if the window is appears to be on the top of
the window stack and is not obstructed by other windows; and "always"
to always try to apply the CopyRect (obstructed regions are clipped
off and not translated).
Note that some desktops (KDE and xfce) appear to mess with the window
stacking in ways that are not yet clear. In these cases x11vnc works
around the problem by applying the CopyRect even if obscuring windows'
data is translated! Use -nowirecopyrect if this yields undesirable
effects for your desktop.
Also, the CopyRect encoding may give incorrect results under -scale
(depending on the scale factor the CopyRect operation is often only
approximate: the correctly scaled framebuffer will be slightly
different from the translated one). Use -nowirecopyrect if this or
other painting errors are unacceptable.
Q-51: Does x11vnc support the X DAMAGE Xserver extension to find
modified regions of the screen quickly and efficiently?
Yes, as of Mar/2005 in the libvncserver CVS x11vnc will use the X
DAMAGE extension by default if it is available on the display. This
requires libXdamage to be available in the build environment as well
(recent Linux distros and Solaris 10 have it).
The DAMAGE extension enables the X server to report changed regions of
the screen back to x11vnc. So x11vnc doesn't have to guess where the
changes are (by polling the entire screen every 1 or 2 seconds). The
use of X DAMAGE dramatically reduces the load when the screen is not
changing very much (i.e. most of the time). It also noticeably
improves updates, especially for very small changed areas (e.g. clock
ticking, cursor flashing, typing, etc).
Note that the DAMAGE extension does not speed up the actual reading of
pixels from the video card framebuffer memory, by, say, mirroring them
in main memory. So reading the fb is still painfully slow (e.g.
5MB/sec), and so even using X DAMAGE when large changes occur on the
screen the bulk of the time is still spent retrieving them.
Unfortunately the current Xorg DAMAGE extension implementation can at
times be overly cautious and report very large rectangles as "damaged"
even though only a small portion of the pixels have actually been
modified. This behavior is often the fault of the window manager (e.g.
it redraws the entire, unseen, frame window underneath the application
window when it gains focus), or the application itself (e.g. does
large, unnecessary repaints).
To work around this deficiency, x11vnc currently only trusts small
DAMAGE rectangles to contain real damage. The larger rectangles are
only used as hints to focus the traditional scanline polling (i.e. if
a scanline doesn't intersect a recent DAMAGE rectangle, the scan is
skipped). You can use the "[302]-xd_area A" option to adjust the size
of the trusted DAMAGE rectangles. The default is 20000 pixels (e.g. a
140x140 square, etc). Use "-xd_area 0" to disable the cutoff and trust
all DAMAGE rectangles.
The option "[303]-xd_mem f" may also be of use in tuning the
algorithm. To disable using DAMAGE entirely use "[304]-noxdamage".
[Mouse Cursor Shapes]
Q-52: Why isn't the mouse cursor shape (the little icon shape where
the mouse pointer is) correct as I move from window to window?
On X servers supporting XFIXES or Solaris/IRIX Overlay extensions it
is possible for x11vnc to do this correctly. See the paragraphs below.
Historically, the X11 mouse cursor shape (i.e. little picture: an
arrow, X, I-beam, resizer, etc) is one of the few write-only objects
in X11. That is, an application can tell the X server what the cursor
shape should be when the pointer is in a given window, but a program
(like x11vnc) unfortunately cannot read this information. I believe
this is because the cursor shape is often downloaded to the graphics
hardware (video card), but I could be mistaken.
A simple kludge is provided by the "[305]-cursor X" option that
changes the cursor when the mouse is on the root background (or any
window has the same cursor as the root background). Note that desktops
like GNOME or KDE often cover up the root background, so this won't
work for those cases. Also see the "[306]-cursor some" option for
additional kludges.
Note that as of Aug/2004 in the libvncserver CVS, on Solaris using the
SUN_OVL overlay extension and IRIX, x11vnc can show the correct mouse
cursor when the [307]-overlay option is supplied. See [308]this FAQ
for more info.
Also as of Dec/2004 in the libvncserver CVS XFIXES X extension support
has been added to allow exact extraction of the mouse cursor shape.
XFIXES fixes the problem of the cursor-shape being write-only: x11vnc
can now query the X server for the current shape and send it back to
the connected viewers. XFIXES is available on recent Linux Xorg based
distros and [309]Solaris 10.
The only XFIXES issue is the handling of alpha channel transparency in
cursors. If a cursor has any translucency then in general it must be
approximated to opaque RGB values. There are some situations where the
cursor transparency can also handled exactly: when the VNC Viewer
requires the cursor shape be drawn into the VNC framebuffer or if you
apply a patch to your VNC Viewer to extract hidden alpha channel data
under 32bpp. [310]Details can be found here.
Q-53: When using XFIXES cursorshape mode, some of the cursors look
really bad with extra black borders around the cursor and other cruft.
How can I improve their appearance?
This happens for cursors with transparency ("alpha channel"); regular
X cursors (bitmaps) should be correct. Unfortunately x11vnc 0.7 was
released with a very poor algorithm for approximating the
transparency, which led to the ugly black borders.
The problem is as follows: XFIXES allows x11vnc to retrieve the
current X server cursor shape, including the alpha channel for
transparency. For traditional bitmap cursors the alpha value will be 0
for completely transparent pixels and 255 for completely opaque
pixels; whereas for modern, eye-candy cursors an alpha value between 0
and 255 means to blend in the background colors to that degree with
the cursor colors. The pixel color blending formula is something like
this: Red = Red_cursor * a + Red_background * (1 - a), (where here 0
=< a =< 1), with similar for Green and Blue. The VNC protocol does not
currently support an alpha channel in cursors: it only supports
regular X bitmap cursors and Rich Cursors that have RGB (Red, Green,
Blue) color data, but no "A" = alpha data. So in general x11vnc has to
approximate a cursor with transparency to create a Rich Cursor. This
is easier said than done: some cursor themes have cursors with
complicated drop shadows and other forms of translucency.
Anyway, for the x11vnc 0.7.1 release the algorithm for approximating
transparency is much improved and hopefully gives decent cursor shapes
for most cursor themes and you don't have to worry about it.
In case it still looks bad for your cursor theme, there are (of
course!) some tunable parameters. The "[311]-alphacut n" option lets
you set the threshold "n" (between 0 and 255): cursor pixels with
alpha values below n will be considered completely transparent while
values equal to or above n will be completely opaque. The default is
240. The "[312]-alphafrac f" option tries to correct individual
cursors that did not fare well with the default -alphacut value: if a
cursor has less than fraction f (between 0.0 and 1.0) of its pixels
selected by the default -alphacut, the threshold is lowered until f of
its pixels are selected. The default fraction is 0.33.
Finally, there is an option [313]-alpharemove that is useful for
themes where many cursors are light colored (e.g. "whiteglass").
XFIXES returns the cursor data with the RGB values pre-multiplied by
the alpha value. If the white cursors look too grey, specify
-alpharemove to brighten them by having x11vnc divide out the alpha
value.
Q-54: In XFIXES mode, are there any hacks to handle cursor
transparency ("alpha channel") exactly?
As of Jan/2005 in the CVS, libvncserver has been modified to allow an
alpha channel (i.e. RGBA data) for Rich Cursors. So x11vnc can now
send the alpha channel data to libvncserver. However, this data will
only be used for VNC clients that do not support the
CursorShapeUpdates VNC extension (or have disabled it). It can be
disabled for all clients with the [314]-nocursorshape x11vnc option.
In this case the cursor is drawn, correctly blended with the
background, into the VNC framebuffer before being sent out to the
client. So the alpha blending is done on the x11vnc side. Use the
[315]-noalphablend option to disable this behavior (always approximate
transparent cursors with opaque RGB values).
The CursorShapeUpdates VNC extension complicates matters because the
cursor shape is sent to the VNC viewers supporting it, and the viewers
draw the cursor locally. This improves response over slow links. Alpha
channel data for these locally drawn cursors is not supported by the
VNC protocol.
However, in the libvncserver CVS there is a patch to the TightVNC
viewer to make this work for CursorShapeUpdates under some
circumstances. This hack is outside of the VNC protocol. It requires
the screens on both sides to be depth 24 at 32bpp (it uses the extra 8
bits to secretly hide the cursor alpha channel data). Not only does it
require depth 24 at 32bpp, but it also currently requires the client
and server to be of the same endianness (otherwise the hidden alpha
data gets reset to zero by a libvncserver translation function; we can
fix this at some point if there is interest). The patch is for the
TightVNC 1.3dev5 Unix vncviewer and it enables the TightVNC viewer to
do the cursor alpha blending locally. The patch code should give an
example on how to change the Windows TightVNC viewer to achieve the
same thing (send me the patch if you get that working).
[Mouse Pointer]
Q-55: Why does the mouse arrow just stay in one corner in my
vncviewer, whereas my cursor (that does move) is just a dot?
This default takes advantage of a [316]tightvnc extension
(CursorShapeUpdates) that allows specifying a cursor image shape for
the local VNC viewer. You may disable it with the [317]-nocursor
option to x11vnc if your viewer does not have this extension.
Note: as of Aug/2004 in the libvncserver CVS this should be fixed: the
default for non-tightvnc viewers (or ones that do not support
CursorShapeUpdates) will be to draw the moving cursor into the x11vnc
framebuffer. This can also be disabled via -nocursor.
Q-56: Can I take advantage of the TightVNC extension to the VNC
protocol where Cursor Positions Updates are sent back to all connected
clients (i.e. passive viewers can see the mouse cursor being moved
around by another viewer)?
Use the [318]-cursorpos option when starting x11vnc. A VNC viewer must
support the Cursor Positions Updates for the user to see the mouse
motions (the TightVNC viewers support this). As of Aug/2004 in the
libvncserver CVS -cursorpos is the default. See also [319]-nocursorpos
and [320]-nocursorshape.
Q-57: Is it possible to swap the mouse buttons (e.g. left-handed
operation), or arbitrarily remap them? How about mapping button clicks
to keystrokes, e.g. to partially emulate Mouse wheel scrolling?
You can remap the mouse buttons via something like: [321]-buttonmap
13-31 (or perhaps 12-21). Also, note that xmodmap(1) lets you directly
adjust the X server's button mappings, but in some circumstances it
might be more desirable to have x11vnc do it.
One user had an X server with only one mouse button(!) and was able to
map all of the VNC client mouse buttons to it via: -buttonmap 123-111.
Note that the [322]-debug_pointer option prints out much info for
every mouse/pointer event and is handy in solving problems.
To map mouse button clicks to keystrokes you can use the alternate
format where the keystrokes are enclosed between colons like this
:<KeySym>: in place of the mouse button digit. For a sequence of
keysyms separate them with "+" signs. Look in the include file
<X11/keysymdef.h>, or use xev(1), or -debug_keyboard to fine the
keysym names. Button clicks can also be included in the sequence via
the fake keysyms Button1, etc.
As an example, suppose the VNC viewer machine has a mouse wheel (these
generate button 4 and 5 events), but the machine that x11vnc is run on
only has the 3 regular buttons. In normal operation x11vnc will
discard the button 4 and 5 events. However, either of the following
button maps could possibly be of use emulating the mouse wheel events
in this case:
-buttonmap 12345-123:Prior::Next:
-buttonmap 12345-123:Up+Up+Up::Down+Down+Down:
Exactly what keystroke "scrolling" events they should be bound to
depends on one's taste. If this method is too approximate, one could
consider not using [323]-buttonmap but rather configuring the X server
to think it has a mouse with 5 buttons even though the physical mouse
does not.
Note that when a keysym-mapped mouse button is clicked down this
immediately generates the key-press and key-release events (for each
keysym in turn if the mapping has a sequence of keysyms). When the
mouse button goes back up nothing is generated.
If you include modifier keys like Shift_L instead of key-press
immediately followed by key-release the state of the modifier key is
toggled (however the initial state of the modifier key is ignored). So
to map the right button to type my name 'Karl Runge' I could use this:
-buttonmap 3-:Shift_L+k+Shift_L+a+r+l+space+Shift_L+r+Shift_L+u+n+g+e:
(yes, this is getting a little silly).
[Keyboard Issues]
Q-58: How can I get my AltGr and Shift modifiers to work between
keyboards for different languages?
The option [324]-modtweak should be of some use for this. It is a mode
that monitors the state of the Shift and AltGr Modifiers and tries to
deduce the correct keycode to send, possibly by sending fake modifier
key presses and releases in addition to the actual keystroke.
Update: As of Jul/2004 in the libvncserver CVS, -modtweak is now the
default (use -nomodtweak to get the old behavior). This was done
because it was noticed on newer XFree86 setups even on bland "us"
keyboards like "pc104 us" XFree86 included a "ghost" key with both "<"
and ">" it. This key does not exist on the keyboard (see [325]this FAQ
for more info). Without -modtweak there was then an ambiguity in the
reverse map keysym => keycode, making it so the "<" symbol could not
be typed.
Also see the [326]FAQ about the -xkb option for a more powerful method
of modifier tweaking for use on X servers with the XKEYBOARD
extension.
When trying to resolve keyboard mapping problems, note that the
[327]-debug_keyboard option prints out much info for every keystroke
and so can be useful debugging things.
Q-59: When I try to type a "<" (i.e. less than) instead I get ">"
(i.e. greater than)! Strangely, typing ">" works OK!!
Does your keyboard have a single key with both "<" and ">" on it? Even
if it doesn't, your X server may think your keyboard has such a key
(e.g. pc105 in the XF86Config file when it should be something else,
say pc104).
The problem here is that on the Xserver where x11vnc is run there are
two keycodes that correspond to the "<" keysym. Run something like
this to see:
xmodmap -pk | egrep -i 'KeyCode|less|greater'
There are 4 KeySyms per KeyCode; KeyCodes range from 8 to 255.
KeyCode Keysym (Keysym) ...
59 0x002c (comma) 0x003c (less)
60 0x002e (period) 0x003e (greater)
94 0x003c (less) 0x003e (greater)
That keycode 94 is the special key with both "<" and ">". When x11vnc
receives the "<" keysym over the wire from the remote VNC client, it
unfortunately maps it to keycode 94 instead of 59, and sends 94 to the
X server. Since Shift is down (i.e. you are Shifting the comma key),
the X server interprets this as Shifted-94, which is ">".
A workaround in the X server configuration is to "deaden" that special
key:
xmodmap -e "keycode 94 = "
However, one user said he had to do this:
xmodmap -e "keycode 94 = 0x002c 0x003c"
(If the numerical values are different for your setup, substitute the
ones that correspond to your display. The above xmodmap scheme can
often be used to work around other ambiguous keysym to keycode
mappings).
Alternatively, here are some x11vnc options to try to work around the
problem:
-modtweak
and
-remap less-comma
These are convenient in that they do not modify the actual X server
settings. The former ([328]-modtweak) is a mode that monitors the
state of the Shift and AltGr modifiers and tries to deduce the correct
keycode sequence to send. Since Jul/2004 -modtweak is now the default.
The latter ([329]-remap less-comma) is an immediate remapping of the
keysym less to the keysym comma when it comes in from a client (so
when Shift is down the comma press will yield "<").
See also the [330]FAQ about the -xkb option as a possible workaround
using the XKEYBOARD extension.
Note that the [331]-debug_keyboard option prints out much info for
every keystroke to aid debugging keyboard problems.
Q-60: I'm using an "international" keyboard (e.g. German "de", or
Danish "dk") and the -modtweak mode works well if the VNC viewer is
run on a Unix/Linux machine with a similar keyboard. But if I run
the VNC viewer on Unix/Linux with a different keyboard (e.g. "us") or
Windows with any keyboard, I can't type some keys like: "@", "$",
"<", ">", etc. How can I fix this?
The problem with Windows is it does not seem to handle AltGr well. It
seems to fake it up by sending Control_L+Alt_R to applications. The
Windows VNC viewer sends those two down keystrokes out on the wire to
the VNC server, but when the user types the next key to get, e.g., "@"
the Windows VNC viewer sends events bringing the up the
Control_L+Alt_R keys, and then sends the "@" keysym by itself.
The Unix/Linux VNC viewer on a "us" keyboard does a similar thing
since "@" is the Shift of the "2" key. The keysyms Shift and "@" are
sent to the VNC server.
In both cases no AltGr is sent to the VNC server, but we know AltGr is
needed on the physical international keyboard to type a "@".
This all worked fine with x11vnc running with the [332]-modtweak
option (it figures out how to adjust the Modifier keys (Shift or
AltGr) to get the "@"). However it fails under recent versions of
XFree86 (and the X.org fork). These run the XKEYBOARD extension by
default and make heavy use of it to handle international keyboards.
To make a long story short, on these newer XFree86 setups the
traditional X keymap lookup x11vnc uses is no longer accurate. x11vnc
can't find the keysym "@" anywhere in the keymapping! (even though it
is in the XKEYBOARD extended keymapping).
How to Solve: As of Jul/2004 in the libvncserver CVS x11vnc has two
changes:
* -modtweak (tweak Modifier keys) is now the default (use
-nomodtweak to go back to the old way)
* there is a new option -xkb to use the XKEYBOARD extension API to
do the Modifier key tweaking.
The [333]-xkb option seems to fix all of the missing keys: "@", "<",
">", etc.: it is recommended that you try it if you have this sort of
problem. Let us know if there are any remaining problems (see the next
paragraph for some known problems). If you specify the -debug_keyboard
(aka -dk) option twice you will get a huge amount of keystroke
debugging output (send it along with any problems you report).
Known problems:
* One user had to disable a "ghost" Mode_switch key that was causing
problems under -xkb. His physical AltGr key was bound to
ISO_Level3_Shift (which seems to be the XKEYBOARD way of doing
things), while there was a ghost key Mode_switch (which seems to
be obsolete) in the mapping as well. Both of these keysyms were
bound to Mod5 and x11vnc was unfortunately choosing Mode_switch.
From the x11vnc -xkb -dk -dk output it was noted that Mode_switch
was attached to keycode 93 (no physical key generates this
keycode) while ISO_Level3_Shift was attached to keycode 113. The
keycode skipping option was used to disable the ghost key:
[334]-skip_keycodes 93
* In implementing -xkb we noticed that some characters were still
not getting through, e.g. "~" and "^". This is not really an
XKEYBOARD problem. What was happening was the VNC viewer was
sending the keysyms asciitilde and asciicircum to x11vnc, but on
the X server with the international keyboard those keysyms were
not mapped to any keys. So x11vnc had to skip them.
The way these characters are typically entered on international
keyboards is by "dead" (aka "mute") keys. E.g. to enter "~" at the
physical display the keysym dead_tilde is pressed and released
(this usually involves holding AltGr down while another key is
pressed) and then space is pressed. (this can also be used get
characters with the "~" symbol on top, e.g. "<22>" by typing "a"
instead of space).
What to do? In general the VNC protocol has not really solved this
problem: what should be done if the VNC viewer sends a keysym not
recognized by the VNC server side? Workarounds can possibly be
created using the [335]-remap x11vnc option:
-remap asciitilde-dead_tilde,asciicircum-dead_circumflex
etc. Use -remap filename if the list is long. Please send us your
workarounds for this problem on your keyboard. Perhaps we can have
x11vnc adjust automatically at some point. Also see the
[336]-add_keysyms option in the next paragraph.
* To complement the above workaround using the [337]-remap, an
option [338]-add_keysyms was added. This option instructs x11vnc
to bind any unknown Keysyms coming in from VNC viewers to unused
Keycodes in the X server. This modifies the global state of the X
server. When x11vnc exits it removes the extra keymappings it
created. Note that the -remap mappings are applied first, right
when the Keysym is received from a VNC viewer, and only after that
would -add_keysyms, or anything else, come into play.
Q-61: When typing I sometimes get double, triple, or more of my
keystrokes repeated. I'm sure I only typed them once, what can I do?
This may be due to an interplay between your X server's key autorepeat
delay and the extra time delays caused by x11vnc processing.
Short answer: disable key autorepeating by running the command "xset r
off" on the Xserver where x11vnc is run (restore via "xset r on") or
use the new (Jul/2004) [339]-norepeat x11vnc option. You will still
have autorepeating because that is taken care of on your VNC viewer
side. Update: as of Dec/2004 -norepeat is now the default. Use -repeat
to disable it.
Details: suppose you press a key DOWN and it generates changes in
large regions of the screen. The CPU and I/O work x11vnc does for the
large screen change could be longer than your X server's key
autorepeat delay. x11vnc may not get to processing the key UP event
until after the screen work is completed. The X server believes the
key has been held down all this time, and applies its autorepeat
rules.
Even without inducing changes in large regions of the screen, this
problem could arise when accessing x11vnc via a dialup modem or
otherwise high latency link (e.g. > 250 ms latency).
Look at the output of "xset q" for the "auto repeat delay" setting. Is
it low (e.g. < 300 ms)? If you turn off autorepeat completely: "xset r
off", does the problem go away?
The workaround is to manually apply "xset r off" and "xset r on" as
needed, or to use the [340]-norepeat (which has since Dec/2004 been
made the default). Note that with X server autorepeat turned off the
VNC viewer side of the connection will (nearly always) do its own
autorepeating so there is no big loss here, unless someone is also
working at the physical display and misses his autorepeating.
Q-62: The x11vnc -norepeat mode is in effect, but I still get repeated
keystrokes!!
Are you using x11vnc to log in to an X session? (as described in
[341]this FAQ) If so, x11vnc is starting before your session and it
disables autorepeat when you connect, but then after you log in your
session startup (GNOME, KDE, ...) could be resetting the autorepeat to
be on. Or it could be something inside your desktop trying to be
helpful that decides to turn it back on.
x11vnc in -norepeat mode will by default reset autorepeat to off 2
times (to help get thru the session startup problem), but it will not
continue to battle with things turning autorepeat back on. It will
also turn autorepeat off whenever it goes from a state of zero clients
to one client. You can adjust the number of resets via "-norepeat N",
or use "-norepeat -1" to have it keep resetting it whenever autorepeat
gets turned back on when clients are connected.
In general you can manually turn autorepeating off by typing "xset r
off", or a using desktop utility/menu, or "x11vnc -R norepeat". If
something in your desktop is automatically turning it back on you
should figure out how to disable that somehow.
Q-63: The machine where I run x11vnc has an AltGr key, but the local
machine where I run the VNC viewer does not. Is there a way I can map
a local unused key to send an AltGr? How about a Compose key as well?
Something like "[342]-remap Super_R-Mode_switch" x11vnc option may
work. Note that Super_R is the "Right Windoze(tm) Flaggie" key; you
may want to choose another. The -debug_keyboard option comes in handy
in finding keysym names (so does xev(1)).
For Compose how about "-remap Menu-Multi_key" (note that Multi_key is
the official name for Compose). To do both at the same time: "-remap
Super_R-Mode_switch,Menu-Multi_key" or use "-remap filename" to
specify remappings from a file.
Q-64: I have a Sun machine I run x11vnc on. Its Sun keyboard has just
one Alt key labelled "Alt" and two Meta keys labelled with little
diamonds. The machine where I run the VNC viewer only has Alt keys.
How can I send a Meta keypress? (e.g. emacs needs this)
Here are a couple ideas. The first one is to simply use xmodmap(1) to
adjust the Sun X server. Perhaps xmodmap -e "keysym Alt_L = Meta_L
Alt_L" will do the trick. (there are other ways to do it, one user
used: xmodmap -e "keycode 26 = Meta_L" for his setup).
Since xmodmap(1) modifies the X server mappings you may not want to do
this (because it affects local work on that machine). Something like
the [343]-remap Alt_L-Meta_L to x11vnc may be sufficient for ones
needs, and does not modify the X server environment. Note that you
cannot send Alt_L in this case, maybe -remap Super_L-Meta_L would be a
better choice if the Super_L key is typically unused.
Q-65: Can I map a keystroke to a mouse button click on the remote
machine?
This can be done directly in some X servers using AccessX and
Pointer_EnableKeys, but is a bit awkward. It may be more convenient to
have x11vnc do the remapping. This can be done via the [344]-remap
option using the fake "keysyms" Button1, Button2, etc. as the "to"
keys (i.e. the ones after the "-")
As an example, consider a laptop where the VNC viewer is run that has
a touchpad with only two buttons. It is difficult to do a middle
button "paste" because (using XFree86 Emulate3Buttons) you have to
click both buttons on the touch pad at the same time. This remapping:
[345]-remap Super_R-Button2
maps the Super_R "flag" key press to the Button2 click, thereby making
X pasting a bit easier.
Note that once the key goes down, the button down and button up events
are generated immediately on the x11vnc side. When the key is released
(i.e. goes up) no events are generated.
[Screen Related Issues and Features]
Q-66: The remote display is larger (in number of pixels) than the
local display I am running the vncviewer on. I don't like the
vncviewer scrollbars, what I can do?
vncviewer has a option (usually accessible via F8 key or -fullscreen
option) for vncviewer to run in full screen, where it will
automatically scroll when the mouse is near the edge of the current
view. For quick scrolling, also make sure Backing Store is enabled on
the machine vncviewer is run on. (XFree86 disables it by default for
some reason, add Option "backingstore" to XF86Config on the vncviewer
side).
BTW, contact me if you are having problems with vncviewer in
fullscreen mode with your window manager (i.e. no keyboard response).
I have a workaround for vncviewer using XGrabServer().
There may also be scaling viewers out there (e.g. TightVNC on Windows)
that automatically shrink or expand the remote framebuffer to fit the
local display. Especially for hand-held devices. See also [346]this
FAQ on x11vnc scaling.
Q-67: Does x11vnc support server-side framebuffer scaling? (E.g. to
make the desktop smaller).
As of Jun/2004 in the libvncserver CVS x11vnc provides basic
server-side scaling. It is a global scaling of the desktop, not a
per-client setting. To enable it use the "[347]-scale fraction"
option. "fraction" can either be a floating point number (e.g. -scale
0.5) or the alternative m/n fraction notation (e.g. -scale 2/3). Note
that if fraction is greater than one the display is magnified.
Extra resources (CPU, memory I/O, and memory) are required to do the
scaling. If the machine is slow where x11vnc is run with scaling
enabled, the interactive response can be unacceptable. OTOH, if run
with scaling on a fast machine the performance degradation is usually
not a big issue or even noticeable.
Also, if you just want a quick, rough "thumbnail" of the display you
can append ":nb" to the fraction to turn on "no blending" mode. E.g.:
"-scale 1/3:nb" Fonts will be difficult to read, but the larger
features will be recognizable. BTW, "no blending" mode is forced on
when scaling 8bpp PseudoColor displays (because blending an indexed
colormap is a bad idea and leads to random colors).
One can also use the ":nb" with an integer scale factor (say "-scale
2:nb") to use x11vnc as a screen magnifier for vision impaired
[348]applications. Since with integer scale factors the framebuffers
become huge and scaling operations time consuming, be sure to use
":nb" for the fastest response.
In general for a scaled display if you are using a TightVNC viewer you
may want to turn off jpeg encoding (e.g. vncviewer -nojpeg host:0).
There appears to be a noise enhancement effect, especially for regions
containing font/text: the scaling can introduce some pixel artifacts
that evidently causes the tight encoding algorithm to incorrectly
detect the regions as image data and thereby introduce additional
pixel artifacts due to the lossiness of the jpeg compression
algorithm. Experiment to see if -nojpeg vncviewer option improves the
readability of text when using -scale to shrink the display size. Also
note that scaling may actually slow down the transfer of text regions
because after being scaled they do not compress as well. (this can
often be a significant slowdown, e.g. 10X).
Another issue is that it appears VNC viewers require the screen width
to be a multiple of 4. When scaling x11vnc will round the width to the
nearest multiple of 4. To disable this use the ":n4" sub option (like
":nb" in the previous paragraph; to specify both use a comma:
":nb,n4", etc.)
If one desires per-client scaling for something like 1:1 from a
workstation and 1:2 from a smaller device (e.g. handheld), currently
the only option is to run two (or more) x11vnc processes with
different scalings listening on separate ports ([349]-rfbport option,
etc.).
As of Mar/2005 in the libvncserver CVS x11vnc now scales the mouse
cursor with the same scale factor as the screen. If you don't want
that, use the [350]"-scale_cursor frac" option to set the cursor
scaling to a different factor (e.g. use "-scale_cursor 1" to keep the
cursor at its natural unscaled size).
Q-68: Does x11vnc work with Xinerama? (i.e. multiple monitors joined
together to form one big, single screen).
Yes, it should generally work because it simply polls the big
effective screen. If the viewing-end monitor is not as big as the
remote Xinerama display, then the vncviewer scrollbars, etc, will have
to be used to pan across the large area.
There are a couple potential issues however. If the screen is not
rectangular (e.g. 1280x1024 and 1024x768 monitors joined together),
then there will be "non-existent" areas on the screen. The X server
will return "garbage" image data for these areas and so they may be
distracting to the viewer. The [351]-blackout x11vnc option allows you
to blacken-out rectangles by specifying their WxH+X+Y geometries. If
your system has the libXinerama library, the [352]-xinerama x11vnc
option can be used to have it automatically determine the rectangles
to be blackened out. (Note on 8bpp PseudoColor displays the fill color
may not be black).
Some users have reported that the mouse does not behave properly for
their Xinerama display: i.e. the mouse cannot be moved to all regions
of the large display. If this happens try using the [353]-xwarppointer
option. This instructs x11vnc to fake mouse pointer motions using the
XWarpPointer function instead of the XTestFakeMotionEvent XTEST
function. (This may be due to a bug in the X server for XTEST when
Xinerama is enabled).
Q-69: Can I use x11vnc on a multi-headed display that is not Xinerama
(i.e. separate screens :0.0, :0.1, ... for each monitor)?
You can, but it is a little bit awkward: you must start separate
x11vnc processes for each screen, and on the viewing end start up
separate VNC viewer processes connecting to them. e.g. on the remote
end:
x11vnc -display :0.0 -bg -q -rfbport 5900
x11vnc -display :0.1 -bg -q -rfbport 5901
(this could be automated in the display manager Xsetup for example)
and then on the local machine where you are sitting:
vncviewer somehost:0 &
vncviewer somehost:1 &
Note: if you are running on Solaris 8 or earlier you can easily hit up
against the maximum of 6 shm segments per process (for Xsun in this
case) from running multiple x11vnc processes. You should modify
/etc/system as mentioned in another [354]FAQ to increase the limit. It
is probably also a good idea to run with the [355]-onetile option in
this case (to limit each x11vnc to 3 shm segments), or even
[356]-noshm to use no shm segments.
Q-70: Can x11vnc show only a portion of the display? (E.g. for a
special purpose rfb application).
As of Mar/2005 in the libvncserver CVS x11vnc has the "[357]-clip
WxH+X+Y" option to select a rectangle of width W, height H and offset
(X, Y). Thus the VNC screen will be the clipped sub-region of the
display and be only WxH in size.
This also works to view a sub-region of a single application window if
the [358]-id or [359]-sid options are used. The offset is measured
from the upper left corner of the selected window.
Q-71: Does x11vnc support the XRANDR (X Resize, Rotate and Reflection)
extension? Whenever I rotate or resize the screen x11vnc just seems to
crash.
As of Dec/2004 in the libvncserver CVS x11vnc supports XRANDR. You
enable it with the [360]-xrandr option to make x11vnc monitor XRANDR
events and also trap X server errors if the screen change occurred in
the middle of an X call like XGetImage. Once it traps the screen
change it will create a new framebuffer using the new screen. If the
connected vnc viewers support the NewFBSize VNC extension (Windows
TightVNC viewer and RealVNC 4.0 windows and Unix viewers do) then the
viewer will automatically resize. Otherwise, the new framebuffer is
fit as best as possible into the original viewer size (portions of the
screen may be clipped, unused, etc). For these viewers you can try the
[361]-padgeom option to make the region big enough to hold all resizes
and rotations.
If you specify "-xrandr newfbsize" then vnc viewers that do not
support NewFBSize will be disconnected before the resize. If you
specify "-xrandr exit" then all will be disconnected and x11vnc will
terminate.
Q-72: Why is the view in my VNC viewer completely black? Or why is
everything flashing around randomly?
See the next FAQ for a possible explanation.
Q-73: I use Linux Virtual Consoles (VC's) to implement 'Fast User
Switching' between users' sessions (e.g. Betty is on Ctrl-Alt-F7,
Bobby is on Ctrl-Alt-F8, and Sid is on Ctrl-Alt-F1: they use those
keystrokes to switch between their sessions). How come the view in a
VNC viewer connecting to x11vnc is either completely black or
otherwise all messed up unless the X session x11vnc is attached to is
in the active VC?
This seems to have to do with how applications (the X server processes
in this case) must "play nicely" if they are not on the active VC.
That is, they should not read from the keyboard or mouse or manage the
video display unless they have the active VC. Given that it appears
the XGetImage() call must ultimately retrieve the framebuffer data
from the video hardware itself, it would make sense x11vnc's polling
wouldn't work unless the X session had active control of the VC.
There does not seem to be an easy way to work around this. Even xwd(1)
doesn't work in this case (try it). Something would need to be done at
a lower level, say in the XFree86 X server. Also, using the XFree86
Shadow Framebuffer (a copy of the video framebuffer is kept in main
memory) does not appear to fix the problem.
If no one is sitting at the workstation and you just want to remotely
switch the VC over to the one associated with your X session (so
x11vnc can poll it correctly), one can use the chvt(1) command, e.g.
"chvt 7" for VC #7.
Q-74: Can I use x11vnc to view my VMWare session remotely?
Yes, since VMWare is an X application you can view it via x11vnc in
the normal way.
Note that VMWare has several viewing modes:
* Normal X application window (with window manager frame)
* Quick-Switch mode (with no window manager frame)
* Fullscreen mode
The way VMWare does Fullscreen mode on Linux is to display the Guest
desktop in a separate Virtual Console (e.g. VC 8) (see [362]this FAQ
on VC's for background). Unfortunately, this Fullscreen VC is not an X
server. So x11vnc cannot access it (however, [363]see this for a
possible partial workaround). x11vnc works fine with "Normal X
application window" and "Quick-Switch mode" because these use X.
One user reports he left his machine with VMWare in the Fullscreen
mode, and even though his X session wasn't in the active VC, he could
still connect x11vnc to the X session and pass the keystrokes Ctrl-Alt
(typing "blind") to the VMWare X app. This induced VMWare to switch
out of Fullscreen into Normal X mode and he could continue working in
the Guest desktop remotely.
Sometimes it is convenient (for performance, etc.) to start VMWare in
its own X session using startx(1). This can be used to have a minimal
window manger (e.g. twm or even no window manager), to improve
response. One can also cut the display depth (e.g. to 16bpp) in this
2nd X session to improve video performance. This 2nd X session
emulates Fullscreen mode to some degree and can be viewed via x11vnc
as long as the VMWare X session [364]is in the active VC.
Also note that with a little bit of playing with "xwininfo -all
-children" output one can extract the (non-toplevel) windowid of the
of the Guest desktop only when VMWare is running as a normal X
application. Then one can export just the guest desktop (i.e. without
the VMWare menu buttons) by use of the [365]-id windowid option. The
caveats are the X session VMWare is in must be in the active VC and
the window must be fully visible, so this mode is not terribly
convenient, but could be useful in some circumstances (e.g. running
VMWare on a very powerful server machine in a server room that happens
to have a video card, (but need not have a monitor, Keyboard or
mouse)).
Q-75: Can non-X devices (e.g. a raw framebuffer) be viewed and/or
controlled by x11vnc?
As of Apr/2005 in the libvncserver CVS there is rudimentary support
for this. Two options were added: "-rawfb string" (to indicate the raw
framembuffer and its parameters) and "-pipeinput cmd" (to provide an
external program that will inject or otherwise process mouse and
keystroke input).
This non-X mode for x11vnc is experimental because it is so removed in
scope from the intended usage of the tool. No attempt is made to make
all of the other options consistent with non-X framebuffer polling. So
all of the X-related options (e.g. -add_keysyms, -xkb) are just
ignored or in the worst case will cause a crash. Be careful applying
such an option via the command line or remote control.
The format for the -rawfb string is:
-rawfb <type>:<object>@<W>x<H>x<bpp>[:<R>/<G>/<B>][+<offset>]
Some examples:
-rawfb shm:210337933@800x600x32:ff/ff00/ff0000
-rawfb map:/dev/fb0@1024x768x16
-rawfb map:/tmp/Xvfb_screen0@640x480x8+3232
-rawfb file:/tmp/my.pnm@250x200x24+37
So the type can be "shm" for shared memory objects, and "map" or
"file" for file objects. "map" uses mmap(2) to map the file into
memory and is preferred over "file" (that uses the slower lseek(2)
access method). Only use file if map isn't working. BTW, "mmap" is an
alias for "map" and if you do not supply a type and the file exists,
map is assumed.
Also, if the string is of the form "setup:cmd" then cmd is run and the
first line of its output retrieved and used as the rawfb string. This
allows initializing the device, determining WxHxB, etc.
The object will be the numerical shared memory id for the case of shm.
The idea here is some other program has created this shared memory
segment and periodically updates it with new framebuffer data. x11vnc
polls the area for changes. See shmat(2) and ipcs(8) for more info.
The ipcs command will list current shared memory segments on the
system.
The object will be the path to the regular or character special file
for the cases of map and file. The idea here is that in the case of a
regular file some other program is writing/updating framebuffer image
data to it. In the case of a character special (e.g. /dev/fb0) it is
the kernel that is "updating" the framebuffer data.
In all cases x11vnc needs to be told the width, height, and number of
bits per pixel (bpp) of the framebuffer. This is the @WxHxB field. For
the case of the Linux framebuffer device, /dev/fb0, the fbset(8) may
be of use (but may not always be accurate for what is currently
viewable). In general some guessing may be required, especially for
the bpp.
Based on the bpp x11vnc will try to guess the red, green, and blue
masks (these indicate which bits correspond to each color). It if gets
it wrong you can specify them manually via the optional ":R/G/B"
field. E.g. ":0xff000/0x00ff00/0x0000ff" (this is the default for
32bpp).
Finally, the framebuffer may not begin at the beginning of the memory
object, so use the optional "+offset" parameter to indicate where the
framebuffer information starts. So as an example, the Xvfb virtual
framebuffer has options -shmem and -fbdir for exporting its virtual
screen to either shm or a mapped file. The format of these is XWD and
so the initial header should be skipped. BTW, since XWD is not
strictly RGB the view will only be approximate. Of course for the case
of Xvfb x11vnc can poll it much better via the [366]X API, but you get
the idea.
By default in -rawfb mode x11vnc will actually close any X display it
happened to open. This is basically to shake out bugs (e.g it will
crash rather than mysteriously interacting with the X display). If you
want x11vnc to keep the X display open while polling the raw
framebuffer capitalize the type (i.e. "SHM:", "MAP:", or "FILE:").
This could be convenient for keeping the remote control channel active
(it uses X properties). The "-connect /path/to/file" mechanism could
also be used for remote control to avoid the X property channel. Rare
usage, but if you also supply -noviewonly in this mode then the mouse
and keyboard input are still sent to the X display, presumably for
doing something strange with /dev/fb...
All of the above was just for viewing the raw framebuffer. That may be
enough for certain applications of this feature (e.g. suppose a video
camera mapped its framebuffer into memory). To handle the pointer and
keyboard input from the viewer users the "-pipeinput cmd" option was
added to indicate a helper program to process the user input. The
input is streamed to it and looks something like this:
Pointer 1 205 257 0 None
Pointer 1 198 253 0 None
Pointer 1 198 253 1 ButtonPress-1
Pointer 1 198 253 0 ButtonRelease-1
Pointer 1 198 252 0 None
Keysym 1 1 119 w KeyPress
Keysym 1 0 119 w KeyRelease
Keysym 1 1 65288 BackSpace KeyPress
Keysym 1 0 65288 BackSpace KeyRelease
Keysym 1 1 112 p KeyPress
Keysym 1 0 112 p KeyRelease
Run "-pipeinput tee:/bin/cat" to get a description of the format. Note
that the -pipeinput option is independent of -rawfb mode and so may
have some other interesting uses. BTW, the "tee:" prefix means x11vnc
will both process the user input and pipe it to the command. The
default is to just pipe it to the -pipeinput command.
Note the -pipeinput helper program could actually control the raw
framebuffer. In the libvncserver CVS a simple example program
x11vnc/misc/slide.pl is provided that demonstrates a simple jpeg
"slideshow" application.
The -pipeinput program is run with these environment variables set:
X11VNC_PID, X11VNC_PROG, X11VNC_CMDLINE, X11VNC_RAWFB_STR to aid its
knowing what is up.
Another example provided in libvncserver CVS is a script to inject
keystrokes into the Linux console (e.g. the virtual consoles:
/dev/tty1, /dev/tty2, etc) in x11vnc/misc/vcinject.pl. It is based on
the vncterm/LinuxVNC.c program also in the libvncserver CVS. So to
view and interact with VC #2 (assuming it is the [367]active VC) one
can run something like:
x11vnc -rawfb map:/dev/fb0@1024x768x16 -pipeinput './vcinject.pl 2'
This assumes your Linux framebuffer device (/dev/fb0) is properly
configured. See fbset(8) and other documentation. Try
"file:/dev/fb0@WxHxB" as a last resort.
The above is just an example of what can be done. If you really want
to view and interact with the Linux console it is better to use the
more accurate and faster LinuxVNC program. The only advantage x11vnc
-rawfb might have is that it can presumably allow interaction with a
non-text application, e.g. one based on svgalib. For example the
[368]VMWare Fullscreen mode is actually viewable under -rawfb. But
this isn't much use until one figures out how to inject keystrokes and
mouse events.
The -rawfb and -pipeinput features are intended to help one creatively
"get out of a jam" (say on a legacy or embedded device) where X is
absent or doesn't work properly. Feedback and bug reports are welcome.
For more control and less overhead use libvncserver in your own C
program that passes the framebuffer to libvncserver.
Q-76: I am using x11vnc where my local machine has "popup/hidden
taskbars" (e.g. GNOME or MacOS X) and the remote display where x11vnc
runs also has "popup/hidden taskbars" (e.g. GNOME). When I move the
mouse to the edge of the screen where the popups happen, the taskbars
interfere and fight with each other in strange ways. What can I do?
Is there a way to temporarily disable one or both of these magic
desktop taskbars? One x11vnc user suggests: it should be
straightforward to right mouse click on the task bar panel, and
uncheck "enable auto-hide" from the panel properties dialog box. This
will make the panel always visible.
[Misc: Clipboard, Beeps, Thanks, etc.]
Q-77: Does the Clipboard/Selection get transferred between the
vncviewer and the X display?
As of Jan/2004 in the libvncserver CVS x11vnc supports the "CutText"
part of the rfb protocol. Furthermore, x11vnc is able to hold the
PRIMARY selection (Xvnc does not seem to do this). If you don't want
the Clipboard/Selection exchanged use the [369]-nosel option. If you
don't want the PRIMARY selection to be polled for changes use the
[370]-noprimary option.
You may need to watch out for desktop utilities such as KDE's
"Klipper" that do odd things with the selection, clipboard, and
cutbuffers.
Q-78: Why don't I hear the "Beeps" in my X session (e.g. when typing
tput bel in an xterm)?
As of Dec/2003 in the libvncserver CVS "Beep" XBell events are tracked
by default. The X server must support the XKEYBOARD extension (this is
not on by default in Solaris, see Xserver(1) for how to turn it on via
+kb), and so you won't hear them if the extension is not present.
If you don't want to hear the beeps use the [371]-nobell option. If
you want to hear the audio from the remote applications, consider
trying a redirector such as esd.
Contributions:
Q-79: Thanks for your program and for your help! Can I make a
donation?
Please do (any amount is appreciated) and thank you for your support!
Click on the PayPal button below for more info.
Also, in general I always enjoy hearing from x11vnc users, how they
use it, what new features they would like, etc. Please send me an
[372]email!
[PayPal]
References
1. http://www.karlrunge.com/x11vnc/index.html#faq
2. http://www.karlrunge.com/x11vnc/index.html#downloading
3. http://www.karlrunge.com/x11vnc/index.html#building
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85. http://www.karlrunge.com/x11vnc/index.html#faq-transients-id
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99. http://www.karlrunge.com/x11vnc/index.html#faq-ssh-unix
100. http://www.karlrunge.com/x11vnc/index.html#faq-ssh-putty
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134. http://www.karlrunge.com/x11vnc/index.html#faq-scrollbars
135. http://www.karlrunge.com/x11vnc/index.html#faq-scaling
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144. http://www.karlrunge.com/x11vnc/index.html#faq-hidden-taskbars
145. http://www.karlrunge.com/x11vnc/index.html#faq-clipboard
146. http://www.karlrunge.com/x11vnc/index.html#faq-beeps
147. http://www.karlrunge.com/x11vnc/index.html#faq-thanks
148. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-display
149. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-auth
150. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-users
151. http://www.karlrunge.com/x11vnc/index.html#solarisbuilding
152. http://www.karlrunge.com/x11vnc/x11vnc_sunos4.html
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154. http://www.karlrunge.com/x11vnc/index.html#faq-build
155. http://packages.debian.org/x11vnc
156. http://www.linuxpackages.net/search_view.php?by=name&name=x11vnc
157. http://dag.wieers.com/packages/x11vnc/
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159. http://www.sunfreeware.com/
160. http://www.bell-labs.com/project/wwexptools/packages.html
161. http://www.karlrunge.com/x11vnc/index.html#solarisbuilding
162. http://www.karlrunge.com/x11vnc/bins
163. http://www.tightvnc.com/download.html
164. http://www.realvnc.com/download-free.html
165. http://sourceforge.net/projects/cotvnc/
166. http://www.karlrunge.com/x11vnc/x11vnc_opts.html
167. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-gui
168. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-q
169. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-bg
170. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-o
171. http://www.karlrunge.com/x11vnc/x11vnc.c
172. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-sigpipe
173. http://www.karlrunge.com/x11vnc/index.html#solarisbuilding
174. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-nofb
175. http://fredrik.hubbe.net/x2vnc.html
176. http://www.hubbe.net/~hubbe/win2vnc.html
177. http://www.deboer.gmxhome.de/
178. http://sourceforge.net/projects/win2vnc/
179. http://fredrik.hubbe.net/x2vnc.html
180. http://freshmeat.net/projects/x2x/
181. http://ftp.digital.com/pub/Digital/SRC/x2x/
182. http://zapek.com/software/zvnc/
183. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-visual
184. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-flashcmap
185. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-notruecolor
186. http://www.karlrunge.com/x11vnc/index.html#faq-8bpp
187. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-overlay
188. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-overlay
189. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-id
190. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-overlay
191. http://www.karlrunge.com/x11vnc/index.html#faq-overlays
192. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-id
193. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-sid
194. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-display
195. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-noshm
196. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-flipbyteorder
197. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-auth
198. http://www.karlrunge.com/x11vnc/index.html#xauth_pain
199. http://www.karlrunge.com/x11vnc/index.html#faq-noshm
200. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-remote
201. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-query
202. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-forever
203. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-bg
204. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-clear_mods
205. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-clear_keys
206. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-remote
207. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-query
208. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-gui
209. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-storepasswd
210. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-rfbauth
211. http://www.karlrunge.com/x11vnc/index.html#faq-passwdfile
212. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-viewpasswd
213. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-passwd
214. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-passwdfile
215. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-rfbauth
216. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-input
217. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-forever
218. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-shared
219. http://www.karlrunge.com/x11vnc/index.html#tunnelling
220. http://www.karlrunge.com/x11vnc/index.html#faq-passwd
221. http://www.karlrunge.com/x11vnc/index.html#faq-passwdfile
222. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-allow
223. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-localhost
224. http://www.karlrunge.com/x11vnc/index.html#faq-tcp_wrappers
225. http://www.karlrunge.com/x11vnc/index.html#faq-inetd
226. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-listen
227. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-allow
228. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-localhost
229. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-allow
230. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-localhost
231. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-listen
232. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-allow
233. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-localhost
234. http://www.karlrunge.com/x11vnc/index.html#tunnelling
235. http://www.karlrunge.com/x11vnc/index.html#tunnelling
236. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-localhost
237. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-rfbauth
238. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-passwdfile
239. http://www.karlrunge.com/x11vnc/index.html#tunnelling
240. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-connect
241. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-accept
242. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-viewonly
243. ftp://ftp.x.org/
244. http://www.karlrunge.com/x11vnc/dtVncPopup
245. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-gone
246. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-localhost
247. http://www.karlrunge.com/x11vnc/index.html#tunnelling
248. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-accept
249. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-users
250. http://www.karlrunge.com/x11vnc/blockdpy.c
251. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-accept
252. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-gone
253. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-gone
254. http://www.karlrunge.com/x11vnc/index.html#display-manager-continuously
255. http://www.karlrunge.com/x11vnc/index.html#faq-inetd
256. http://www.karlrunge.com/x11vnc/index.html#x11vnc_loop
257. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-auth
258. http://www.karlrunge.com/x11vnc/index.html#dtlogin_solaris
259. http://www.jirka.org/gdm-documentation/x241.html
260. http://www.karlrunge.com/x11vnc/x11vnc_loop
261. http://www.karlrunge.com/x11vnc/index.html#faq-xterminal-xauth
262. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-inetd
263. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-q
264. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-auth
265. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-httpdir
266. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-connect
267. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-vncconnect
268. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-add_keysyms
269. http://www.karlrunge.com/x11vnc/index.html#display-manager-continuously
270. http://www.karlrunge.com/x11vnc/shm_clear
271. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-onetile
272. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-noshm
273. http://www.karlrunge.com/x11vnc/index.html#faq-noshm
274. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-nap
275. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-wait
276. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-onetile
277. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-fs
278. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-threads
279. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-defer
280. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-id
281. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-solid
282. http://www.tightvnc.com/
283. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-nodragging
284. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-progressive
285. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-fs
286. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-wait
287. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-defer
288. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-id
289. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-nosel
290. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-nocursor
291. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-nocursorpos
292. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-pointer_mode
293. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-pointer_mode
294. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-nodragging
295. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-pointer_mode
296. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-threads
297. http://www.karlrunge.com/x11vnc/index.html#faq-wireframe
298. http://www.karlrunge.com/x11vnc/index.html#faq-pointer-mode
299. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-wireframe
300. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-wireframe
301. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-wireframe
302. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-xd_area
303. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-xd_mem
304. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-noxdamage
305. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-cursor
306. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-cursor
307. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-overlay
308. http://www.karlrunge.com/x11vnc/index.html#the-overlay-mode
309. http://www.karlrunge.com/x11vnc/index.html#solaris10-build
310. http://www.karlrunge.com/x11vnc/index.html#faq-xfixes-alpha-hacks
311. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-alphacut
312. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-alphafrac
313. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-alpharemove
314. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-nocursorshape
315. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-noalphablend
316. http://www.tightvnc.com/
317. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-nocursor
318. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-cursorpos
319. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-nocursorpos
320. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-nocursorshape
321. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-buttonmap
322. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-debug_pointer
323. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-buttonmap
324. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-modtweak
325. http://www.karlrunge.com/x11vnc/index.html#faq-greaterless
326. http://www.karlrunge.com/x11vnc/index.html#faq-xkbmodtweak
327. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-debug_keyboard
328. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-modtweak
329. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-remap
330. http://www.karlrunge.com/x11vnc/index.html#faq-xkbmodtweak
331. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-debug_keyboard
332. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-modtweak
333. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-xkb
334. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-skip_keycodes
335. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-remap
336. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-add_keysyms
337. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-remap
338. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-add_keysyms
339. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-norepeat
340. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-norepeat
341. http://www.karlrunge.com/x11vnc/index.html#faq-display-manager
342. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-remap
343. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-remap
344. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-remap
345. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-remap
346. http://www.karlrunge.com/x11vnc/index.html#faq-scaling
347. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-scale
348. http://www.cus.cam.ac.uk/~ssb22/source/vnc-magnification.html
349. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-rfbport
350. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-scale_cursor
351. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-blackout
352. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-xinerama
353. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-xwarppointer
354. http://www.karlrunge.com/x11vnc/index.html#faq-solshm
355. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-onetile
356. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-noshm
357. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-clip
358. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-id
359. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-id
360. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-xrandr
361. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-padgeom
362. http://www.karlrunge.com/x11vnc/index.html#faq-linuxvc
363. http://www.karlrunge.com/x11vnc/index.html#faq-rawfb
364. http://www.karlrunge.com/x11vnc/index.html#faq-linuxvc
365. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-id
366. http://www.karlrunge.com/x11vnc/index.html#faq-xvfb
367. http://www.karlrunge.com/x11vnc/index.html#faq-linuxvc
368. http://www.karlrunge.com/x11vnc/index.html#faq-vmware
369. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-nosel
370. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-noprimary
371. http://www.karlrunge.com/x11vnc/x11vnc_opts.html#opt-nobell
372. mailto:xvml@karlrunge.com
=======================================================================
http://www.karlrunge.com/x11vnc/x11vnc_opts.html:
_________________________________________________________________
x11vnc: a VNC server for real X displays
Here are all of x11vnc command line options:
% x11vnc -opts (see below for -help long descriptions)
x11vnc: allow VNC connections to real X11 displays. 0.7.2 lastmod: 2005-05-17
x11vnc options:
-display disp -auth file
-id windowid -sid windowid
-clip WxH+X+Y -flashcmap
-shiftcmap n -notruecolor
-visual n -overlay
-overlay_nocursor -scale fraction
-scale_cursor frac -viewonly
-shared -once
-forever -timeout n
-inetd -http
-connect string -vncconnect
-novncconnect -allow host1[,host2..]
-localhost -nolookup
-input string -viewpasswd string
-passwdfile filename -storepasswd pass file
-accept string -gone string
-users list -noshm
-flipbyteorder -onetile
-solid [color] -blackout string
-xinerama -xtrap
-xrandr [mode] -padgeom WxH
-o logfile -flag file
-rc filename -norc
-h, -help -?, -opts
-V, -version -dbg
-q -bg
-modtweak -nomodtweak
-xkb -noxkb
-skip_keycodes string -skip_dups
-noskip_dups -add_keysyms
-noadd_keysyms -clear_mods
-clear_keys -remap string
-norepeat -repeat
-nofb -nobell
-nosel -noprimary
-cursor [mode] -nocursor
-arrow n -noxfixes
-alphacut n -alphafrac fraction
-alpharemove -noalphablend
-nocursorshape -cursorpos
-nocursorpos -xwarppointer
-buttonmap string -nodragging
-wireframe [str] -nowireframe
-wirecopyrect mode -nowirecopyrect
-debug_wireframe -scrollcopyrect mode
-noscrollcopyrect -scr_area n
-scr_skip list -scr_inc list
-scr_keys list -scr_term list
-scr_parms string -debug_scroll
-pointer_mode n -input_skip n
-speeds rd,bw,lat -debug_pointer
-debug_keyboard -defer time
-wait time -wait_ui factor
-nowait_bog -readtimeout n
-nap -nonap
-sb time -noxdamage
-xd_area A -xd_mem f
-sigpipe string -threads
-nothreads -fs f
-gaps n -grow n
-fuzz n -debug_tiles
-snapfb -rawfb string
-pipeinput cmd -gui [gui-opts]
-remote command -query variable
-sync -noremote
-yesremote -unsafe
-safer -privremote
-nocmds -deny_all
libvncserver options:
-rfbport port TCP port for RFB protocol
-rfbwait time max time in ms to wait for RFB client
-rfbauth passwd-file use authentication on RFB protocol
(use 'storepasswd' to create a password file)
-passwd plain-password use authentication
(use plain-password as password, USE AT YOUR RISK)
-deferupdate time time in ms to defer updates (default 40)
-desktop name VNC desktop name (default "LibVNCServer")
-alwaysshared always treat new clients as shared
-nevershared never treat new clients as shared
-dontdisconnect don't disconnect existing clients when a new non-shared
connection comes in (refuse new connection instead)
-httpdir dir-path enable http server using dir-path home
-httpport portnum use portnum for http connection
-enablehttpproxy enable http proxy support
-progressive height enable progressive updating for slow links
-listen ipaddr listen for connections only on network interface with
addr ipaddr. '-listen localhost' and hostname work too.
% x11vnc -help
x11vnc: allow VNC connections to real X11 displays. 0.7.2 lastmod: 2005-05-17
Typical usage is:
Run this command in a shell on the remote machine "far-host"
with X session you wish to view:
x11vnc -display :0
Then run this in another window on the machine you are sitting at:
vncviewer far-host:0
Once x11vnc establishes connections with the X11 server and starts listening
as a VNC server it will print out a string: PORT=XXXX where XXXX is typically
5900 (the default VNC server port). One would next run something like
this on the local machine: "vncviewer hostname:N" where "hostname" is
the name of the machine running x11vnc and N is XXXX - 5900, i.e. usually
"vncviewer hostname:0".
By default x11vnc will not allow the screen to be shared and it will exit
as soon as the client disconnects. See -shared and -forever below to override
these protections. See the FAQ on how to tunnel the VNC connection through
an encrypted channel such as ssh(1).
For additional info see: http://www.karlrunge.com/x11vnc/
and http://www.karlrunge.com/x11vnc/#faq
Rudimentary config file support: if the file $HOME/.x11vncrc exists then each
line in it is treated as a single command line option. Disable with -norc.
For each option name, the leading character "-" is not required. E.g. a
line that is either "forever" or "-forever" may be used and are equivalent.
Likewise "wait 100" or "-wait 100" are acceptable and equivalent lines.
The "#" character comments out to the end of the line in the usual way.
Leading and trailing whitespace is trimmed off. Lines may be continued with
a "\" as the last character of a line (it becomes a space character).
Options:
-display disp X11 server display to connect to, usually :0. The X
server process must be running on same machine and
support MIT-SHM. Equivalent to setting the DISPLAY
environment variable to "disp".
-auth file Set the X authority file to be "file", equivalent to
setting the XAUTHORITY environment variable to "file"
before startup. Same as -xauth file. See Xsecurity(7),
xauth(1) man pages for more info.
-id windowid Show the window corresponding to "windowid" not
the entire display. New windows like popup menus,
transient toplevels, etc, may not be seen or may be
clipped. Disabling SaveUnders or BackingStore in the
X server may help show them. x11vnc may crash if the
window is initially partially obscured, changes size,
is iconified, etc. Some steps are taken to avoid this
and the -xrandr mechanism is used to track resizes. Use
xwininfo(1) to get the window id, or use "-id pick"
to have x11vnc run xwininfo(1) for you and extract
the id. The -id option is useful for exporting very
simple applications (e.g. the current view on a webcam).
-sid windowid As -id, but instead of using the window directly it
shifts a root view to it: this shows SaveUnders menus,
etc, although they will be clipped if they extend beyond
the window.
-clip WxH+X+Y Only show the sub-region of the full display that
corresponds to the rectangle with size WxH and offset
+X+Y. The VNC display has size WxH (i.e. smaller than
the full display). This also works for -id/-sid mode
where the offset is relative to the upper left corner
of the selected window.
-flashcmap In 8bpp indexed color, let the installed colormap flash
as the pointer moves from window to window (slow).
-shiftcmap n Rare problem, but some 8bpp displays use less than 256
colorcells (e.g. 16-color grayscale, perhaps the other
bits are used for double buffering) *and* also need to
shift the pixels values away from 0, .., ncells. "n"
indicates the shift to be applied to the pixel values.
To see the pixel values set DEBUG_CMAP=1 to print out
a colormap histogram. Example: -shiftcmap 240
-notruecolor For 8bpp displays, force indexed color (i.e. a colormap)
even if it looks like 8bpp TrueColor (rare problem).
-visual n Experimental option: probably does not do what you
think. It simply *forces* the visual used for the
framebuffer; this may be a bad thing... (e.g. messes
up colors or cause a crash). It is useful for testing
and for some workarounds. n may be a decimal number,
or 0x hex. Run xdpyinfo(1) for the values. One may
also use "TrueColor", etc. see <X11/X.h> for a list.
If the string ends in ":m" then for better or for
worse the visual depth is forced to be m.
-overlay Handle multiple depth visuals on one screen, e.g. 8+24
and 24+8 overlay visuals (the 32 bits per pixel are
packed with 8 for PseudoColor and 24 for TrueColor).
Currently -overlay only works on Solaris via
XReadScreen(3X11) and IRIX using XReadDisplay(3).
On Solaris there is a problem with image "bleeding"
around transient popup menus (but not for the menu
itself): a workaround is to disable SaveUnders
by passing the "-su" argument to Xsun (in
/etc/dt/config/Xservers). Also note that the mouse
cursor shape is exactly correct in this mode.
Use -overlay as a workaround for situations like these:
Some legacy applications require the default visual to
be 8bpp (8+24), or they will use 8bpp PseudoColor even
when the default visual is depth 24 TrueColor (24+8).
In these cases colors in some windows will be messed
up in x11vnc unless -overlay is used. Another use of
-overlay is to enable showing the exact mouse cursor
shape (details below).
Under -overlay, performance will be somewhat degraded
due to the extra image transformations required.
For optimal performance do not use -overlay, but rather
configure the X server so that the default visual is
depth 24 TrueColor and try to have all apps use that
visual (e.g. some apps have -use24 or -visual options).
-overlay_nocursor Sets -overlay, but does not try to draw the exact mouse
cursor shape using the overlay mechanism.
-scale fraction Scale the framebuffer by factor "fraction". Values
less than 1 shrink the fb, larger ones expand it. Note:
image may not be sharp and response may be slower.
If "fraction" contains a decimal point "." it
is taken as a floating point number, alternatively
the notation "m/n" may be used to denote fractions
exactly, e.g. -scale 2/3
Scaling Options: can be added after "fraction"
via ":", to supply multiple ":" options use
commas. If you just want a quick, rough scaling
without blending, append ":nb" to "fraction"
(e.g. -scale 1/3:nb). No blending is the default
for 8bpp indexed color, to force blending for this
case use ":fb". For compatibility with vncviewers
the scaled width is adjusted to be a multiple of 4:
to disable this use ":n4". More esoteric options:
":in" use interpolation scheme even when shrinking,
":pad", pad scaled width and height to be multiples
of scaling denominator (e.g. 3 for 2/3).
-scale_cursor frac By default if -scale is supplied the cursor shape is
scaled by the same factor. Depending on your usage,
you may want to scale the cursor independently of the
screen or not at all. If you specify -scale_cursor
the cursor will be scaled by that factor. When using
-scale mode to keep the cursor at its "natural" size
use "-scale_cursor 1". Most of the ":" scaling
options apply here as well.
-viewonly All VNC clients can only watch (default off).
-shared VNC display is shared (default off).
-once Exit after the first successfully connected viewer
disconnects, opposite of -forever. This is the Default.
-forever Keep listening for more connections rather than exiting
as soon as the first client(s) disconnect. Same as -many
-timeout n Exit unless a client connects within the first n seconds
of startup.
-inetd Launched by inetd(1): stdio instead of listening socket.
Note: if you are not redirecting stderr to a log file
(via shell 2> or -o option) you must also specify the
-q option, otherwise the stderr goes to the viewer.
-http Instead of using -httpdir (see below) to specify
where the Java vncviewer applet is, have x11vnc try
to *guess* where the directory is by looking relative
to the program location and in standard locations
(/usr/local/share/x11vnc/classes, etc).
-connect string For use with "vncviewer -listen" reverse connections.
If "string" has the form "host" or "host:port"
the connection is made once at startup. Use commas
for a list of host's and host:port's.
If "string" contains "/" it is instead interpreted
as a file to periodically check for new hosts.
The first line is read and then the file is truncated.
Be careful for this usage mode if x11vnc is running as
root (e.g. via inetd(1) or gdm(1)).
-vncconnect Monitor the VNC_CONNECT X property set by the standard
-novncconnect VNC program vncconnect(1). When the property is
set to "host" or "host:port" establish a reverse
connection. Using xprop(1) instead of vncconnect may
work (see the FAQ). Default: -vncconnect
-allow host1[,host2..] Only allow client connections from hosts matching
the comma separated list of hostnames or IP addresses.
Can also be a numerical IP prefix, e.g. "192.168.100."
to match a simple subnet, for more control build
libvncserver with libwrap support (See the FAQ). If the
list contains a "/" it instead is a interpreted as a
file containing addresses or prefixes that is re-read
each time a new client connects. Lines can be commented
out with the "#" character in the usual way.
-localhost Same as "-allow 127.0.0.1".
Note: if you want to restrict which network interface
x11vnc listens on, see the -listen option below.
E.g. "-listen localhost" or "-listen 192.168.3.21".
As a special case, the option "-localhost" implies
"-listen localhost".
For non-localhost -listen usage, if you use the remote
control mechanism (-R) to change the -listen interface
you may need to manually adjust the -allow list (and
vice versa) to avoid situations where no connections
(or too many) are allowed.
-nolookup Do not use gethostbyname() or gethostbyaddr() to look up
host names or IP numbers. Use this if name resolution
is incorrectly set up and leads to long pauses as name
lookup times out, etc.
-input string Fine tuning of allowed user input. If "string" does
not contain a comma "," the tuning applies only to
normal clients. Otherwise the part before "," is
for normal clients and the part after for view-only
clients. "K" is for Keystroke input, "M" for
Mouse-motion input, and "B" for Button-click input.
Their presence in the string enables that type of input.
E.g. "-input M" means normal users can only move
the mouse and "-input KMB,M" lets normal users do
anything and enables view-only users to move the mouse.
This option is ignored when a global -viewonly is in
effect (all input is discarded).
-viewpasswd string Supply a 2nd password for view-only logins. The -passwd
(full-access) password must also be supplied.
-passwdfile filename Specify libvncserver -passwd via the first line of the
file "filename" instead of via command line (where
others might see it via ps(1)). If a second non blank
line exists in the file it is taken as a view-only
password (i.e. -viewpasswd) To supply an empty password
for either field the string "__EMPTY__" may be used.
Note: -passwdfile is a simple plaintext passwd, see
also -rfbauth and -storepasswd below for obfuscated
VNC password files. Neither file should be readable
by others.
-storepasswd pass file Store password "pass" as the VNC password in the
file "file". Once the password is stored the
program exits. Use the password via "-rfbauth file"
-accept string Run a command (possibly to prompt the user at the
X11 display) to decide whether an incoming client
should be allowed to connect or not. "string" is
an external command run via system(3) or some special
cases described below. Be sure to quote "string"
if it contains spaces, shell characters, etc. If the
external command returns 0 the client is accepted,
otherwise the client is rejected. See below for an
extension to accept a client view-only.
If x11vnc is running as root (say from inetd(1) or from
display managers xdm(1), gdm(1), etc), think about the
security implications carefully before supplying this
option (likewise for the -gone option).
Environment: The RFB_CLIENT_IP environment variable will
be set to the incoming client IP number and the port
in RFB_CLIENT_PORT (or -1 if unavailable). Similarly,
RFB_SERVER_IP and RFB_SERVER_PORT (the x11vnc side
of the connection), are set to allow identification
of the tcp virtual circuit. The x11vnc process
id will be in RFB_X11VNC_PID, a client id number in
RFB_CLIENT_ID, and the number of other connected clients
in RFB_CLIENT_COUNT. RFB_MODE will be "accept"
If "string" is "popup" then a builtin popup window
is used. The popup will time out after 120 seconds,
use "popup:N" to modify the timeout to N seconds
(use 0 for no timeout)
If "string" is "xmessage" then an xmessage(1)
invocation is used for the command. xmessage must be
installed on the machine for this to work.
Both "popup" and "xmessage" will present an option
for accepting the client "View-Only" (the client
can only watch). This option will not be presented if
-viewonly has been specified, in which case the entire
display is view only.
If the user supplied command is prefixed with something
like "yes:0,no:*,view:3 mycommand ..." then this
associates the numerical command return code with
the actions: accept, reject, and accept-view-only,
respectively. Use "*" instead of a number to indicate
the default action (in case the command returns an
unexpected value). E.g. "no:*" is a good choice.
Note that x11vnc blocks while the external command
or popup is running (other clients may see no updates
during this period).
More -accept tricks: use "popupmouse" to only allow
mouse clicks in the builtin popup to be recognized.
Similarly use "popupkey" to only recognize
keystroke responses. These are to help avoid the
user accidentally accepting a client by typing or
clicking. All 3 of the popup keywords can be followed
by +N+M to supply a position for the popup window.
The default is to center the popup window.
-gone string As -accept, except to run a user supplied command when
a client goes away (disconnects). RFB_MODE will be
set to "gone" and the other RFB_* variables are as
in -accept. Unlike -accept, the command return code
is not interpreted by x11vnc. Example: -gone 'xlock &'
-users list If x11vnc is started as root (say from inetd(1) or from
display managers xdm(1), gdm(1), etc), then as soon
as possible after connections to the X display are
established try to switch to one of the users in the
comma separated "list". If x11vnc is not running as
root this option is ignored.
Why use this option? In general it is not needed since
x11vnc is already connected to the X display and can
perform its primary functions. The option was added
to make some of the *external* utility commands x11vnc
occasionally runs work properly. In particular under
GNOME and KDE to implement the "-solid color" feature
external commands (gconftool-2 and dcop) must be run
as the user owning the desktop session. Since this
option switches userid it also affects the userid used
to run the processes for the -accept and -gone options.
It also affects the ability to read files for options
such as -connect, -allow, and -remap. Note that the
-connect file is also sometimes written to.
So be careful with this option since in many situations
its use can decrease security.
The switch to a user will only take place if the
display can still be successfully opened as that user
(this is primarily to try to guess the actual owner
of the session). Example: "-users fred,wilma,betty".
Note that a malicious user "barney" by quickly using
"xhost +" when logging in may get x11vnc to switch
to user "fred". What happens next?
Under display managers it may be a long time before
the switch succeeds (i.e. a user logs in). To make
it switch immediately regardless if the display
can be reopened prefix the username with the "+"
character. E.g. "-users +bob" or "-users +nobody".
The latter (i.e. switching immediately to user
"nobody") is probably the only use of this option
that increases security.
To immediately switch to a user *before* connections
to the X display are made or any files opened use the
"=" character: "-users =bob". That user needs to
be able to open the X display of course.
The special user "guess=" means to examine the utmpx
database (see who(1)) looking for a user attached to
the display number (from DISPLAY or -display option)
and try him/her. To limit the list of guesses, use:
"-users guess=bob,betty".
Even more sinister is the special user "lurk=" that
means to try to guess the DISPLAY from the utmpx login
database as well. So it "lurks" waiting for anyone
to log into an X session and then connects to it.
Specify a list of users after the = to limit which
users will be tried. To enable a different searching
mode, if the first user in the list is something like
":0" or ":0-2" that indicates a range of DISPLAY
numbers that will be tried (regardless of whether
they are in the utmpx database) for all users that
are logged in. Examples: "-users lurk=" and also
"-users lurk=:0-1,bob,mary"
Be especially careful using the "guess=" and "lurk="
modes. They are not recommended for use on machines
with untrustworthy local users.
-noshm Do not use the MIT-SHM extension for the polling.
Remote displays can be polled this way: be careful this
can use large amounts of network bandwidth. This is
also of use if the local machine has a limited number
of shm segments and -onetile is not sufficient.
-flipbyteorder Sometimes needed if remotely polled host has different
endianness. Ignored unless -noshm is set.
-onetile Do not use the new copy_tiles() framebuffer mechanism,
just use 1 shm tile for polling. Limits shm segments
used to 3.
-solid [color] To improve performance, when VNC clients are connected
try to change the desktop background to a solid color.
The [color] is optional: the default color is "cyan4".
For a different one specify the X color (rgb.txt name,
e.g. "darkblue" or numerical "#RRGGBB").
Currently this option only works on GNOME, KDE, CDE,
and classic X (i.e. with the background image on the
root window). The "gconftool-2" and "dcop" external
commands are run for GNOME and KDE respectively.
Other desktops won't work, e.g. Xfce (send us the
corresponding commands if you find them). If x11vnc is
running as root (inetd(1) or gdm(1)), the -users option
may be needed for GNOME and KDE. If x11vnc guesses
your desktop incorrectly, you can force it by prefixing
color with "gnome:", "kde:", "cde:" or "root:".
-blackout string Black out rectangles on the screen. "string" is a
comma separated list of WxH+X+Y type geometries for
each rectangle.
-xinerama If your screen is composed of multiple monitors
glued together via XINERAMA, and that screen is
non-rectangular this option will try to guess the
areas to black out (if your system has libXinerama).
In general on XINERAMA displays you may need to use the
-xwarppointer option if the mouse pointer misbehaves.
-xtrap Use the DEC-XTRAP extension for keystroke and mouse
input insertion. For use on legacy systems, e.g. X11R5,
running an incomplete or missing XTEST extension.
By default DEC-XTRAP will be used if XTEST server grab
control is missing, use -xtrap to do the keystroke and
mouse insertion via DEC-XTRAP as well.
-xrandr [mode] If the display supports the XRANDR (X Resize, Rotate
and Reflection) extension, and you expect XRANDR events
to occur to the display while x11vnc is running, this
options indicates x11vnc should try to respond to
them (as opposed to simply crashing by assuming the
old screen size). See the xrandr(1) manpage and run
'xrandr -q' for more info. [mode] is optional and
described below.
Since watching for XRANDR events and trapping errors
increases polling overhead, only use this option if
XRANDR changes are expected. For example on a rotatable
screen PDA or laptop, or using a XRANDR-aware Desktop
where you resize often. It is best to be viewing with a
vncviewer that supports the NewFBSize encoding, since it
knows how to react to screen size changes. Otherwise,
libvncserver tries to do so something reasonable for
viewers that cannot do this (portions of the screen
may be clipped, unused, etc).
"mode" defaults to "resize", which means create a
new, resized, framebuffer and hope all viewers can cope
with the change. "newfbsize" means first disconnect
all viewers that do not support the NewFBSize VNC
encoding, and then resize the framebuffer. "exit"
means disconnect all viewer clients, and then terminate
x11vnc.
-padgeom WxH Whenever a new vncviewer connects, the framebuffer is
replaced with a fake, solid black one of geometry WxH.
Shortly afterwards the framebuffer is replaced with the
real one. This is intended for use with vncviewers
that do not support NewFBSize and one wants to make
sure the initial viewer geometry will be big enough
to handle all subsequent resizes (e.g. under -xrandr,
-remote id:windowid, rescaling, etc.)
-o logfile Write stderr messages to file "logfile" instead of
to the terminal. Same as "-logfile file". To append
to the file use "-oa file" or "-logappend file".
-flag file Write the "PORT=NNNN" (e.g. PORT=5900) string to
"file" in addition to stdout. This option could be
useful by wrapper script to detect when x11vnc is ready.
-rc filename Use "filename" instead of $HOME/.x11vncrc for rc file.
-norc Do not process any .x11vncrc file for options.
-h, -help Print this help text.
-?, -opts Only list the x11vnc options.
-V, -version Print program version and last modification date.
-dbg instead of exiting after cleaning up, run a simple
"debug crash shell" when fatal errors are trapped.
-q Be quiet by printing less informational output to
stderr. Same as -quiet.
-bg Go into the background after screen setup. Messages to
stderr are lost unless -o logfile is used. Something
like this could be useful in a script:
port=`ssh $host "x11vnc -display :0 -bg" | grep PORT`
port=`echo "$port" | sed -e 's/PORT=//'`
port=`expr $port - 5900`
vncviewer $host:$port
-modtweak Option -modtweak automatically tries to adjust the AltGr
-nomodtweak and Shift modifiers for differing language keyboards
between client and host. Otherwise, only a single key
press/release of a Keycode is simulated (i.e. ignoring
the state of the modifiers: this usually works for
identical keyboards). Also useful in resolving cases
where a Keysym is bound to multiple keys (e.g. "<" + ">"
and "," + "<" keys). Default: -modtweak
-xkb When in modtweak mode, use the XKEYBOARD extension (if
-noxkb the X display supports it) to do the modifier tweaking.
This is powerful and should be tried if there are still
keymapping problems when using -modtweak by itself.
The default is to check whether some common keysyms,
e.g. !, @, [, are only accessible via -xkb mode and if
so then automatically enable the mode. To disable this
automatic detection use -noxkb.
-skip_keycodes string Ignore the comma separated list of decimal keycodes.
Perhaps these are keycodes not on your keyboard but
your X server thinks exist. Currently only applies
to -xkb mode. Use this option to help x11vnc in the
reverse problem it tries to solve: Keysym -> Keycode(s)
when ambiguities exist (more than one Keycode per
Keysym). Run 'xmodmap -pk' to see your keymapping.
Example: "-skip_keycodes 94,114"
-skip_dups Some VNC viewers send impossible repeated key events,
-noskip_dups e.g. key-down, key-down, key-up, key-up all for the
same key, or 20 downs in a row for the same key!
Setting -skip_dups means to skip these duplicates and
just process the first event. Default: -skip_dups
-add_keysyms If a Keysym is received from a VNC viewer and
-noadd_keysyms that Keysym does not exist in the X server, then
add the Keysym to the X server's keyboard mapping.
Added Keysyms will be removed periodically and also
when x11vnc exits. Default: -add_keysyms
-clear_mods At startup and exit clear the modifier keys by sending
KeyRelease for each one. The Lock modifiers are skipped.
Used to clear the state if the display was accidentally
left with any pressed down.
-clear_keys As -clear_mods, except try to release any pressed key.
Note that this option and -clear_mods can interfere
with a person typing at the physical keyboard.
-remap string Read Keysym remappings from file named "string".
Format is one pair of Keysyms per line (can be name
or hex value) separated by a space. If no file named
"string" exists, it is instead interpreted as this
form: key1-key2,key3-key4,... See <X11/keysymdef.h>
header file for a list of Keysym names, or use xev(1).
To map a key to a button click, use the fake Keysyms
"Button1", ..., etc. E.g: "-remap Super_R-Button2"
(useful for pasting on a laptop)
Dead keys: "dead" (or silent, mute) keys are keys that
do not produce a character but must be followed by a 2nd
keystroke. This is often used for accenting characters,
e.g. to put "'" on top of "a" by pressing the dead
key and then "a". Note that this interpretation
is not part of core X11, it is up to the toolkit or
application to decide how to react to the sequence.
The X11 names for these keysyms are "dead_grave",
"dead_acute", etc. However some VNC viewers send the
keysyms "grave", "acute" instead thereby disabling
the accenting. To work around this -remap can be used.
For example "-remap grave-dead_grave,acute-dead_acute"
As a convenience, "-remap DEAD" applies these remaps:
g grave-dead_grave
a acute-dead_acute
c asciicircum-dead_circumflex
t asciitilde-dead_tilde
m macron-dead_macron
b breve-dead_breve
D abovedot-dead_abovedot
d diaeresis-dead_diaeresis
o degree-dead_abovering
A doubleacute-dead_doubleacute
r caron-dead_caron
e cedilla-dead_cedilla
If you just want a subset use the first letter
label, e.g. "-remap DEAD=ga" to get the first two.
Additional remaps may also be supplied via commas,
e.g. "-remap DEAD=ga,Super_R-Button2". Finally,
"DEAD=missing" means to apply all of the above as
long as the left hand member is not already in the
X11 keymap.
-norepeat Option -norepeat disables X server key auto repeat when
-repeat VNC clients are connected and VNC keyboard input is
not idle for more than 5 minutes. This works around a
repeating keystrokes bug (triggered by long processing
delays between key down and key up client events: either
from large screen changes or high latency).
Default: -norepeat
Note: your VNC viewer side will likely do autorepeating,
so this is no loss unless someone is simultaneously at
the real X display.
Use "-norepeat N" to set how many times norepeat will
be reset if something else (e.g. X session manager)
disables it. The default is 2. Use a negative value
for unlimited resets.
-nofb Ignore video framebuffer: only process keyboard and
pointer. Intended for use with Win2VNC and x2vnc
dual-monitor setups.
-nobell Do not watch for XBell events. (no beeps will be heard)
Note: XBell monitoring requires the XKEYBOARD extension.
-nosel Do not manage exchange of X selection/cutbuffer between
VNC viewers and the X server.
-noprimary Do not poll the PRIMARY selection for changes to send
back to clients. (PRIMARY is still set on received
changes, however).
-cursor [mode] Sets how the pointer cursor shape (little icon at the
-nocursor mouse pointer) should be handled. The "mode" string
is optional and is described below. The default
is to show some sort of cursor shape(s). How this
is done depends on the VNC viewer and the X server.
Use -nocursor to disable cursor shapes completely.
Some VNC viewers support the TightVNC CursorPosUpdates
and CursorShapeUpdates extensions (cuts down on
network traffic by not having to send the cursor image
every time the pointer is moved), in which case these
extensions are used (see -nocursorshape and -nocursorpos
below to disable). For other viewers the cursor shape
is written directly to the framebuffer every time the
pointer is moved or changed and gets sent along with
the other framebuffer updates. In this case, there
will be some lag between the vnc viewer pointer and
the remote cursor position.
If the X display supports retrieving the cursor shape
information from the X server, then the default is
to use that mode. On Solaris this can be done with
the SUN_OVL extension using -overlay (see also the
-overlay_nomouse option). A similar overlay scheme
is used on IRIX. Xorg (e.g. Linux) and recent Solaris
Xsun servers support the XFIXES extension to retrieve
the exact cursor shape from the X server. If XFIXES
is present it is preferred over Overlay and is used by
default (see -noxfixes below). This can be disabled
with -nocursor, and also some values of the "mode"
option below.
Note that under XFIXES cursors with transparency (alpha
channel) will not be exactly represented and one may
find Overlay preferable. See also the -alphacut and
-alphafrac options below as fudge factors to try to
improve the situation for cursors with transparency
for a given theme.
The "mode" string can be used to fine-tune the
displaying of cursor shapes. It can be used the
following ways:
"-cursor arrow" - just show the standard arrow
nothing more or nothing less.
"-cursor none" - same as "-nocursor"
"-cursor X" - when the cursor appears to be on the
root window, draw the familiar X shape. Some desktops
such as GNOME cover up the root window completely,
and so this will not work, try "X1", etc, to try to
shift the tree depth. On high latency links or slow
machines there will be a time lag between expected and
the actual cursor shape.
"-cursor some" - like "X" but use additional
heuristics to try to guess if the window should have
a windowmanager-like resizer cursor or a text input
I-beam cursor. This is a complete hack, but may be
useful in some situations because it provides a little
more feedback about the cursor shape.
"-cursor most" - try to show as many cursors as
possible. Often this will only be the same as "some"
unless the display has overlay visuals or XFIXES
extensions available. On Solaris and IRIX if XFIXES
is not available, -overlay mode will be attempted.
-arrow n Choose an alternate "arrow" cursor from a set of
some common ones. n can be 1 to 6. Default is: 1
-noxfixes Do not use the XFIXES extension to draw the exact cursor
shape even if it is available.
-alphacut n When using the XFIXES extension for the cursor shape,
cursors with transparency will not be displayed exactly
(but opaque ones will). This option sets n as a cutoff
for cursors that have transparency ("alpha channel"
with values ranging from 0 to 255) Any cursor pixel with
alpha value less than n becomes completely transparent.
Otherwise the pixel is completely opaque. Default 240
Note: the options -alphacut, -alphafrac, and -alphafrac
may be removed if a more accurate internal method for
handling cursor transparency is implemented.
-alphafrac fraction With the threshold in -alphacut some cursors will become
almost completely transparent because their alpha values
are not high enough. For those cursors adjust the
alpha threshold until fraction of the non-zero alpha
channel pixels become opaque. Default 0.33
-alpharemove By default, XFIXES cursors pixels with transparency have
the alpha factor multiplied into the RGB color values
(i.e. that corresponding to blending the cursor with a
black background). Specify this option to remove the
alpha factor. (useful for light colored semi-transparent
cursors).
-noalphablend In XFIXES mode do not send cursor alpha channel data
to libvncserver. The default is to send it. The
alphablend effect will only be visible in -nocursorshape
mode or for clients with cursorshapeupdates turned
off. (However there is a hack for 32bpp with depth 24,
it uses the extra 8 bits to store cursor transparency
for use with a hacked vncviewer that applies the
transparency locally. See the FAQ for more info).
-nocursorshape Do not use the TightVNC CursorShapeUpdates extension
even if clients support it. See -cursor above.
-cursorpos Option -cursorpos enables sending the X cursor position
-nocursorpos back to all vnc clients that support the TightVNC
CursorPosUpdates extension. Other clients will be able
to see the pointer motions. Default: -cursorpos
-xwarppointer Move the pointer with XWarpPointer(3X) instead of
the XTEST extension. Use this as a workaround
if the pointer motion behaves incorrectly, e.g.
on touchscreens or other non-standard setups.
Also sometimes needed on XINERAMA displays.
-buttonmap string String to remap mouse buttons. Format: IJK-LMN, this
maps buttons I -> L, etc., e.g. -buttonmap 13-31
Button presses can also be mapped to keystrokes: replace
a button digit on the right of the dash with :<sym>:
or :<sym1>+<sym2>: etc. for multiple keys. For example,
if the viewing machine has a mouse-wheel (buttons 4 5)
but the x11vnc side does not, these will do scrolls:
-buttonmap 12345-123:Prior::Next:
-buttonmap 12345-123:Up+Up+Up::Down+Down+Down:
See <X11/keysymdef.h> header file for a list of Keysyms,
or use the xev(1) program. Note: mapping of button
clicks to Keysyms may not work if -modtweak or -xkb is
needed for the Keysym.
If you include a modifier like "Shift_L" the
modifier's up/down state is toggled, e.g. to send
"The" use :Shift_L+t+Shift_L+h+e: (the 1st one is
shift down and the 2nd one is shift up). (note: the
initial state of the modifier is ignored and not reset)
To include button events use "Button1", ... etc.
-nodragging Do not update the display during mouse dragging events
(mouse button held down). Greatly improves response on
slow setups, but you lose all visual feedback for drags,
text selection, and some menu traversals. It overrides
any -pointer_mode setting
-wireframe [str] Try to detect window moves or resizes when a mouse
-nowireframe button is held down and show a wireframe instead of
the full opaque window. This is based completely on
heuristics and may not always work: it depends on your
window manager and even how you move things around.
See -pointer_mode below for discussion of the "bogging
down" problem this tries to avoid.
Default: -wireframe
Shorter aliases: -wf [str] and -nowf
The value "str" is optional and, of course, is
packed with many tunable parameters for this scheme:
Format: shade,linewidth,percent,T+B+L+R,t1+t2+t3+t4
Default: 0xff,3,0,32+8+8+8,0.15+0.30+5.0+0.125
If you leave nothing between commas: ",," the default
value is used. If you don't specify enough commas,
the trailing parameters are set to their defaults.
"shade" indicate the "color" for the wireframe,
usually a greyscale: 0-255, however for 16 and 32bpp you
can specify an rgb.txt X color (e.g. "dodgerblue") or
a value > 255 is treated as RGB (e.g. red is 0xff0000).
"linewidth" sets the width of the wireframe in pixels.
"percent" indicates to not apply the wireframe scheme
to windows with area less than this percent of the
full screen.
"T+B+L+R" indicates four integers for how close in
pixels the pointer has to be from the Top, Bottom, Left,
or Right edges of the window to consider wireframing.
This is a speedup to quickly exclude a window from being
wireframed: set them all to zero to not try the speedup
(scrolling and selecting text will likely be slower).
"t1+t2+t3+t4" specify four floating point times in
seconds: t1 is how long to wait for the pointer to move,
t2 is how long to wait for the window to start moving
or being resized (for some window managers this can be
rather long), t3 is how long to keep a wireframe moving
before repainting the window. t4 is the minimum time
between sending wireframe "animations". For a slow
link this might be a better choice: 0.25+0.6+6.0+0.15
-wirecopyrect mode Since the -wireframe mechanism evidently tracks moving
-nowirecopyrect windows accurately, a speedup can be obtained by
telling the VNC viewers to locally copy the translated
window region. This is the VNC CopyRect encoding:
the framebuffer update doesn't need to send the actual
new image data.
Shorter aliases: -wcr [mode] and -nowcr
"mode" can be "never" (same as -nowirecopyrect)
to never try the copyrect, "top" means only do it if
the window was not covered by any other windows, and
"always" means to translate the orginally unobscured
region (this may look odd as the remaining pieces come
in, but helps on a slow link). Default: "always"
Note: there can be painting errors when using -scale
so CopyRect is skipped when scaling unless you specify
-wirecopyrect on the command line or by remote-control.
-debug_wireframe Turn on debugging info printout for the wireframe
heuristics. "-dwf" is an alias. Specify multiple
times for more output.
-scrollcopyrect mode Like -wirecopyrect, but use heuristics to try to guess
-noscrollcopyrect if a window has scrolled its contents (either vertically
or horizontally). This requires the RECORD X extension
to "snoop" on X applications (currently for certain
XCopyArea and XConfigureWindow X protocol requests).
Examples: Hitting <Return> in a terminal window when the
cursor was at the bottom, the text scrolls up one line.
Hitting <Down> arrow in a web browser window, the web
page scrolls up a small amount.
Shorter aliases: -scr [mode] and -noscr
This scheme will not always detect scrolls, but when
it does there is a nice speedup from using the VNC
CopyRect encoding (see -wirecopyrect). The speedup
is both in reduced network traffic and reduced X
framebuffer polling/copying. On the other hand, it may
induce undesired transients (e.g. a terminal cursor
being scrolled up when it should not be) or other
painting errors (window tearing, bunching-up, etc).
These are automatically repaired in a short period
of time. If this is unacceptable disable the feature
with -noscrollcopyrect.
"mode" can be "never" (same as -noscrollcopyrect)
to never try the copyrect, "keys" means to try it
in response to keystrokes only, "mouse" means to
try it in response to mouse events only, "always"
means to do both. Default: "always"
Note: there can be painting errors when using
-scale so CopyRect is skipped when scaling unless
you specify -scrollcopyrect on the command line or
by remote-control.
-scr_area n Set the minimum area in pixels for a rectangle
to be considered for the -scrollcopyrect detection
scheme. This is to avoid wasting the effort on small
rectangles that would be quickly updated the normal way.
E.g. suppose an app updated the position of its skinny
scrollbar first and then shifted the large panel
it controlled. We want to be sure to skip the small
scrollbar and get the large panel. Default: 60000
-scr_skip list Skip scroll detection for applications matching
the comma separated list of strings in "list".
Some applications implement their scrolling in
strange ways where the XCopyArea, etc, also applies
to invisible portions of the window: if we CopyRect
those areas it looks awful during the scroll and
there may be painting errors left after the scroll.
Soffice.bin is the worst known offender.
Use "##" to denote the start of the application class
(e.g. "##XTerm") and "++" to denote the start
of the application instance name (e.g. "++xterm").
The string your list is matched against is of the form
"^^WM_NAME##Class++Instance<same-for-any-subwindows>"
The "xlsclients -la" command will provide this info.
If a pattern is prefixed with "KEY:" it only applies
to Keystroke generated scrolls (e.g. Up arrow). If it
is prefixed with "MOUSE:" it only applies to Mouse
induced scrolls (e.g. dragging on a scrollbar).
Default: ##Soffice.bin
-scr_inc list Opposite of -scr_skip: this list is consulted first
and if there is a match the window will be monitored
via RECORD for scrolls irrespective of -scr_skip.
Use -scr_skip '*' to skip anything that does not match
your -scr_inc. Use -scr_inc '*' to include everything.
-scr_keys list For keystroke scroll detection, only apply the RECORD
heuristics to the comma separated list of keysyms in
"list". You may find the RECORD overhead for every
one of your keystrokes disrupts typing too much, but you
don't want to turn it off completely with "-scr mouse"
and -scr_parms does not work or is too confusing.
The listed keysyms can be numeric or the keysym
names in the <X11/keysymdef.h> header file or from the
xev(1) program. Example: "-scr_keys Up,Down,Return".
One probably wants to have application specific lists
(e.g. for terminals, etc) but that is too icky to think
about for now...
If "list" begins with the "-" character the list
is taken as an exclude list: all keysyms except those
list will be considered. The special string "builtin"
expands to an internal list of keysyms that are likely
to cause scrolls. BTW, by default modifier keys,
Shift_L, Control_R, etc, are skipped since they almost
never induce scrolling by themselves.
-scr_term list Yet another cosmetic kludge. Apply shell/terminal
heuristics to applications matching comma separated list
(same as -scr_skip/-scr_inc). For example an annoying
transient under scroll detection is if you hit Enter in
a terminal shell with full text window, the solid text
cursor block will be scrolled up. So for a short time
there are two (or more) block cursors on the screen.
There are similar scenarios, (e.g. an output line is
duplicated).
These transients are induced by the approximation of
scroll detection (e.g. it detects the scroll, but not
the fact that the block cursor was cleared just before
the scroll). In nearly all cases these transient errors
are repaired when the true X framebuffer is consulted
by the normal polling. But they are distracting, so
what this option provides is extra "padding" near the
bottom of the terminal window: a few extra lines near
the bottom will not be scrolled, but rather updated
from the actual X framebuffer. This usually reduces
the annoying artifacts. Use "none" to disable.
Default: "term"
-scr_parms string Set various parameters for the scrollcopyrect mode.
The format is similar to that for -wireframe and packed
with lots of parameters:
Format: T+B+L+R,t1+t2+t3,s1+s2+s3+s4+s5
Default: 0+64+32+32,0.02+0.10+0.9,0.03+0.06+0.5+0.1+5.0
If you leave nothing between commas: ",," the default
value is used. If you don't specify enough commas,
the trailing parameters are set to their defaults.
"T+B+L+R" indicates four integers for how close in
pixels the pointer has to be from the Top, Bottom, Left,
or Right edges of the window to consider scrollcopyrect.
If -wireframe overlaps it takes precedence. This is a
speedup to quickly exclude a window from being watched
for scrollcopyrect: set them all to zero to not try
the speedup (things like selecting text will likely
be slower).
"t1+t2+t3" specify three floating point times in
seconds that apply to scrollcopyrect detection with
*Keystroke* input: t1 is how long to wait after a key
is pressed for the first scroll, t2 is how long to keep
looking after a Keystroke scroll for more scrolls.
t3 is how frequently to try to update surrounding
scrollbars outside of the scrolling area (0.0 to
disable)
"s1+s2+s3+s4+s5" specify five floating point times
in seconds that apply to scrollcopyrect detection with
*Mouse* input: s1 is how long to wait after a mouse
button is pressed for the first scroll, s2 is how long
to keep waiting for additional scrolls after the first
Mouse scroll was detected. s3 is how frequently to
try to update surrounding scrollbars outside of the
scrolling area (0.0 to disable). s4 is how long to
buffer pointer motion (to try to get fewer, bigger
mouse scrolls). s5 is the maximum time to spend just
updating the scroll window without updating the rest
of the screen.
-debug_scroll Turn on debugging info printout for the scroll
heuristics. "-ds" is an alias. Specify it multiple
times for more output.
-pointer_mode n Various pointer motion update schemes. "-pm" is
an alias. The problem is pointer motion can cause
rapid changes on the screen: consider the rapid changes
when you drag a large window around. Neither x11vnc's
screen polling and vnc compression routines nor the
bandwidth to the vncviewers can keep up these rapid
screen changes: everything will bog down when dragging
or scrolling. So a scheme has to be used to "eat"
much of that pointer input before re-polling the screen
and sending out framebuffer updates. The mode number
"n" can be 0 to 4 and selects one of the schemes
desribed below.
n=0: does the same as -nodragging. (all screen polling
is suspended if a mouse button is pressed.)
n=1: was the original scheme used to about Jan 2004:
it basically just skips -input_skip keyboard or pointer
events before repolling the screen.
n=2 is an improved scheme: by watching the current rate
of input events it tries to detect if it should try to
"eat" additional pointer events before continuing.
n=3 is basically a dynamic -nodragging mode: it detects
when the mouse motion has paused and then refreshes
the display.
n=4 attempts to measures network rates and latency,
the video card read rate, and how many tiles have been
changed on the screen. From this, it aggressively tries
to push screen "frames" when it decides it has enough
resources to do so. NOT FINISHED.
The default n is 2. Note that modes 2, 3, 4 will skip
-input_skip keyboard events (but it will not count
pointer events). Also note that these modes are not
available in -threads mode which has its own pointer
event handling mechanism.
To try out the different pointer modes to see which
one gives the best response for your usage, it is
convenient to use the remote control function, for
example "x11vnc -R pm:4" or the tcl/tk gui (Tuning ->
pointer_mode -> n).
-input_skip n For the pointer handling when non-threaded: try to
read n user input events before scanning display. n < 0
means to act as though there is always user input.
Default: 10
-speeds rd,bw,lat x11vnc tries to estimate some speed parameters that
are used to optimize scheduling (e.g. -pointer_mode
4) and other things. Use the -speeds option to set
these manually. The triple "rd,bw,lat" corresponds
to video h/w read rate in MB/sec, network bandwidth to
clients in KB/sec, and network latency to clients in
milliseconds, respectively. If a value is left blank,
e.g. "-speeds ,100,15", then the internal scheme is
used to estimate the empty value(s).
Note: use this option is currently NOT FINISHED.
Typical PC video cards have read rates of 5-10 MB/sec.
If the framebuffer is in main memory instead of video
h/w (e.g. SunRay, shadowfb, Xvfb), the read rate may
be much faster. "x11perf -getimage500" can be used
to get a lower bound (remember to factor in the bytes
per pixel). It is up to you to estimate the network
bandwith and latency to clients. For the latency the
ping(1) command can be used.
For convenience there are some aliases provided,
e.g. "-speeds modem". The aliases are: "modem" for
6,4,200; "dsl" for 6,100,50; and "lan" for 6,5000,1
-debug_pointer Print debugging output for every pointer event.
-debug_keyboard Print debugging output for every keyboard event.
Same as -dp and -dk, respectively. Use multiple
times for more output.
-defer time Time in ms to wait for updates before sending to client
(deferUpdateTime) Default: 30
-wait time Time in ms to pause between screen polls. Used to cut
down on load. Default: 30
-wait_ui factor Factor by which to cut the -wait time if there
has been recent user input (pointer or keyboard).
Improves response, but increases the load whenever you
are moving the mouse or typing. Default: 2.00
-nowait_bog Do not detect if the screen polling is "bogging down"
and sleep more. Some activities with no user input can
slow things down a lot: consider a large terminal window
with a long build running in it continously streaming
text output. By default x11vnc will try to detect this
(3 screen polls in a row each longer than 0.25 sec with
no user input), and sleep up to 1.5 secs to let things
"catch up". Use this option to disable the detection.
-readtimeout n Set libvncserver rfbMaxClientWait to n seconds. On
slow links that take a long time to paint the first
screen libvncserver may hit the timeout and drop the
connection. Default: 20 seconds.
-nap Monitor activity and if it is low take longer naps
-nonap between screen polls to really cut down load when idle.
Default: take naps
-sb time Time in seconds after NO activity (e.g. screen blank)
to really throttle down the screen polls (i.e. sleep
for about 1.5 secs). Use 0 to disable. Default: 60
-noxdamage Do not use the X DAMAGE extension to detect framebuffer
changes even if it is available. Use -xdamage if your
default is to have it off.
x11vnc's use of the DAMAGE extension: 1) significantly
reduces the load when the screen is not changing much,
and 2) detects changed areas (small ones by default)
more quickly.
Currently the DAMAGE extension is overly conservative
and often reports large areas (e.g. a whole terminal
or browser window) as damaged even though the actual
changed region is much smaller (sometimes just a few
pixels). So heuristics were introduced to skip large
areas and use the damage rectangles only as "hints"
for the traditional scanline polling. The following
tuning parameters are introduced to adjust this
behavior:
-xd_area A Set the largest DAMAGE rectangle area "A" (in
pixels: width * height) to trust as truly damaged:
the rectangle will be copied from the framebuffer
(slow) no matter what. Set to zero to trust *all*
rectangles. Default: 20000
-xd_mem f Set how long DAMAGE rectangles should be "remembered",
"f" is a floating point number and is in units of the
scanline repeat cycle time (32 iterations). The default
(1.0) should give no painting problems. Increase it if
there are problems or decrease it to live on the edge
(perhaps useful on a slow machine).
-sigpipe string Broken pipe (SIGPIPE) handling. "string" can be
"ignore" or "exit". For "ignore" libvncserver
will handle the abrupt loss of a client and continue,
for "exit" x11vnc will cleanup and exit at the 1st
broken connection. Default: "ignore".
-threads Whether or not to use the threaded libvncserver
-nothreads algorithm [rfbRunEventLoop] if libpthread is available
Default: -nothreads
-fs f If the fraction of changed tiles in a poll is greater
than f, the whole screen is updated. Default: 0.75
-gaps n Heuristic to fill in gaps in rows or cols of n or
less tiles. Used to improve text paging. Default: 4
-grow n Heuristic to grow islands of changed tiles n or wider
by checking the tile near the boundary. Default: 3
-fuzz n Tolerance in pixels to mark a tiles edges as changed.
Default: 2
-debug_tiles Print debugging output for tiles, fb updates, etc.
-snapfb Instead of polling the X display framebuffer (fb) for
changes, periodically copy all of X display fb into main
memory and examine that copy for changes. Under some
circumstances this will improve interactive response,
or at least make things look smoother, but in others
(many) it will make the response worse. If the video
h/w fb is such that reading small tiles is very slow
this mode could help. To keep the "framerate" up
the screen size x bpp cannot be too large. Note that
this mode is very wasteful of memory I/O resources
(it makes full screen copies even if nothing changes).
It may be of use in video capture-like applications,
or where window tearing is a problem.
-rawfb string Experimental option, instead of polling X, poll the
memory object specified in "string". For shared
memory segments it is of the form: "shm:N@WxHxB"
which specifies a shmid N and framebuffer Width, Height,
and Bits per pixel. To memory map mmap(2) a file use:
"map:/path/to/a/file@WxHxB". If there is trouble
with mmap, use "file:/..." for slower lseek(2)
based reading. If you do not supply a type "map"
is assumed if the file exists.
If string is "setup:cmd", then the command "cmd"
is run and the first line from it is read and used
as "string". This allows initializing the device,
determining WxHxB, etc. These are often done as root
so take care.
Optional suffixes are ":R/G/B" and "+O" to specify
red, green, and blue masks and an offset into the
memory object. If the masks are not provided x11vnc
guesses them based on the bpp.
Examples:
-rawfb shm:210337933@800x600x32:ff/ff00/ff0000
-rawfb map:/dev/fb0@1024x768x32
-rawfb map:/tmp/Xvfb_screen0@640x480x8+3232
-rawfb file:/tmp/my.pnm@250x200x24+37
(see ipcs(1) and fbset(1) for the first two examples)
All user input is discarded. Most of the X11 (screen,
keyboard, mouse) options do not make sense and many
will cause this mode to crash, so please think twice
before setting/changing them.
If you don't want x11vnc to close the X DISPLAY in
rawfb mode, then capitalize the prefix, SHM:, MAP:,
FILE: Keeping the display open enables the default
remote-control channel, which could be useful. Also,
if you also specify -noviewonly, then the mouse and
keyboard input are still sent to the X display, this
usage should be very rare, i.e. doing something strange
with /dev/fb0.
-pipeinput cmd Another experimental option: it lets you supply
an extern command in "cmd" that x11vnc will pipe
all of the user input events to in a simple format.
In -pipeinput mode by default x11vnc will not process
any of the user input events. If you prefix "cmd"
with "tee:" it will both send them to the pipe
command and process them. For a description of the
format run "-pipeinput tee:/bin/cat". Another prefix
is "reopen" which means to reopen pipe if it exits.
Separate multiple prefixes with commas.
In combination with -rawfb one might be able to
do amusing things (e.g. control non-X devices).
To facilitate this, if -rawfb is in effect then the
value is stored in X11VNC_RAWFB_STR for the pipe command
to use if it wants. Do 'env | grep X11VNC' for more.
-gui [gui-opts] Start up a simple tcl/tk gui based on the the remote
control options -remote/-query described below.
Requires the "wish" program to be installed on the
machine. "gui-opts" is not required: the default is
to start up both the gui and x11vnc with the gui showing
up on the X display in the environment variable DISPLAY.
"gui-opts" can be a comma separated list of items.
Currently there are these types of items: 1) a gui mode,
a 2) gui "simplicity", and 3) the X display the gui
should display on.
1) The gui mode can be "start", "conn", or "wait"
"start" is the default mode above and is not required.
"conn" means do not automatically start up x11vnc,
but instead just try to connect to an existing x11vnc
process. "wait" means just start the gui and nothing
else (you will later instruct the gui to start x11vnc
or connect to an existing one.)
2) The gui simplicity is off by default (a power-user
gui with all options is presented) To start with
something less daunting supply the string "simple"
("ez" is an alias for this). Once the gui is
started you can toggle between the two with "Misc ->
simple_gui".
3) Note the possible confusion regarding the potentially
two different X displays: x11vnc polls one, but you
may want the gui to appear on another. For example, if
you ssh in and x11vnc is not running yet you may want
the gui to come back to you via your ssh redirected X
display (e.g. localhost:10).
Examples: "x11vnc -gui", "x11vnc -gui ez"
"x11vnc -gui localhost:10", "x11vnc -gui conn,host:0"
If you do not specify a gui X display in "gui-opts"
then the DISPLAY environment variable and -display
option are tried (in that order). Regarding the x11vnc
X display the gui will try to connect to, it first
tries -display and then DISPLAY. For example, "x11vnc
-display :0 -gui otherhost:0", will remote control an
x11vnc polling :0 and display the gui on otherhost:0
If you do not intend to start x11vnc from the gui
(i.e. just remote control an existing one), then the
gui process can run on a different machine from the
x11vnc server as long as X permissions, etc. permit
communication between the two.
-remote command Remotely control some aspects of an already running
x11vnc server. "-R" and "-r" are aliases for
"-remote". After the remote control command is
sent to the running server the 'x11vnc -remote ...'
command exits. You can often use the -query command
(see below) to see if the x11vnc server processed your
-remote command.
The default communication channel is that of X
properties (specifically VNC_CONNECT), and so this
command must be run with correct settings for DISPLAY
and possibly XAUTHORITY to connect to the X server
and set the property. Alternatively, use the -display
and -auth options to set them to the correct values.
The running server cannot use the -novncconnect option
because that disables the communication channel.
See below for alternate channels.
For example: 'x11vnc -remote stop' (which is the same as
'x11vnc -R stop') will close down the x11vnc server.
'x11vnc -R shared' will enable shared connections, and
'x11vnc -R scale:3/4' will rescale the desktop.
Note: the more drastic the change induced by the -remote
command, the bigger the chance for bugs or crashes.
Please report reproducible bugs.
The following -remote/-R commands are supported:
stop terminate the server, same as "quit"
"exit" or "shutdown".
ping see if the x11vnc server responds.
Return is: ans=ping:<xdisplay>
blacken try to push a black fb update to all
clients (due to timings a client
could miss it). Same as "zero", also
"zero:x1,y1,x2,y2" for a rectangle.
refresh send the entire fb to all clients.
reset recreate the fb, polling memory, etc.
id:windowid set -id window to "windowid". empty
or "root" to go back to root window
sid:windowid set -sid window to "windowid"
waitmapped wait until subwin is mapped.
nowaitmapped do not wait until subwin is mapped.
clip:WxH+X+Y set -clip mode to "WxH+X+Y"
flashcmap enable -flashcmap mode.
noflashcmap disable -flashcmap mode.
shiftcmap:n set -shiftcmap to n.
notruecolor enable -notruecolor mode.
truecolor disable -notruecolor mode.
overlay enable -overlay mode (if applicable).
nooverlay disable -overlay mode.
overlay_cursor in -overlay mode, enable cursor drawing.
overlay_nocursor disable cursor drawing. same as
nooverlay_cursor.
visual:vis set -visual to "vis"
scale:frac set -scale to "frac"
scale_cursor:f set -scale_cursor to "f"
viewonly enable -viewonly mode.
noviewonly disable -viewonly mode.
shared enable -shared mode.
noshared disable -shared mode.
forever enable -forever mode.
noforever disable -forever mode.
timeout:n reset -timeout to n, if there are
currently no clients, exit unless one
connects in the next n secs.
http enable http client connections.
nohttp disable http client connections.
deny deny any new connections, same as "lock"
nodeny allow new connections, same as "unlock"
connect:host do reverse connection to host, "host"
may be a comma separated list of hosts
or host:ports. See -connect.
disconnect:host disconnect any clients from "host"
same as "close:host". Use host
"all" to close all current clients.
If you know the client internal hex ID,
e.g. 0x3 (returned by "-query clients"
and RFB_CLIENT_ID) you can use that too.
allowonce:host For the next connection only, allow
connection from "host".
allow:hostlist set -allow list to (comma separated)
"hostlist". See -allow and -localhost.
Do not use with -allow /path/to/file
Use "+host" to add a single host, and
use "-host" to delete a single host
localhost enable -localhost mode
nolocalhost disable -localhost mode
listen:str set -listen to str, empty to disable.
nolookup enable -nolookup mode.
lookup disable -nolookup mode.
input:str set -input to "str", empty to disable.
client_input:str set the K, M, B -input on a per-client
basis. select which client as for
disconnect, e.g. client_input:host:MB
or client_input:0x2:K
accept:cmd set -accept "cmd" (empty to disable).
gone:cmd set -gone "cmd" (empty to disable).
noshm enable -noshm mode.
shm disable -noshm mode (i.e. use shm).
flipbyteorder enable -flipbyteorder mode, you may need
to set noshm for this to do something.
noflipbyteorder disable -flipbyteorder mode.
onetile enable -onetile mode. (you may need to
set shm for this to do something)
noonetile disable -onetile mode.
solid enable -solid mode
nosolid disable -solid mode.
solid_color:color set -solid color (and apply it).
blackout:str set -blackout "str" (empty to disable).
See -blackout for the form of "str"
(basically: WxH+X+Y,...)
Use "+WxH+X+Y" to append a single
rectangle use "-WxH+X+Y" to delete one
xinerama enable -xinerama mode. (if applicable)
noxinerama disable -xinerama mode.
xtrap enable -xtrap input mode.
noxtrap disable -xtrap input mode.
xrandr enable -xrandr mode. (if applicable)
noxrandr disable -xrandr mode.
xrandr_mode:mode set the -xrandr mode to "mode".
padgeom:WxH set -padgeom to WxH (empty to disable)
If WxH is "force" or "do" the padded
geometry fb is immediately applied.
quiet enable -quiet mode.
noquiet disable -quiet mode.
modtweak enable -modtweak mode.
nomodtweak enable -nomodtweak mode.
xkb enable -xkb modtweak mode.
noxkb disable -xkb modtweak mode.
skip_keycodes:str enable -xkb -skip_keycodes "str".
skip_dups enable -skip_dups mode.
noskip_dups disable -skip_dups mode.
add_keysyms enable -add_keysyms mode.
noadd_keysyms stop adding keysyms. those added will
still be removed at exit.
clear_mods enable -clear_mods mode and clear them.
noclear_mods disable -clear_mods mode.
clear_keys enable -clear_keys mode and clear them.
noclear_keys disable -clear_keys mode.
remap:str set -remap "str" (empty to disable).
See -remap for the form of "str"
(basically: key1-key2,key3-key4,...)
Use "+key1-key2" to append a single
keymapping, use "-key1-key2" to delete.
norepeat enable -norepeat mode.
repeat disable -norepeat mode.
nofb enable -nofb mode.
fb disable -nofb mode.
bell enable bell (if supported).
nobell disable bell.
nosel enable -nosel mode.
sel disable -nosel mode.
noprimary enable -noprimary mode.
primary disable -noprimary mode.
cursor:mode enable -cursor "mode".
show_cursor enable showing a cursor.
noshow_cursor disable showing a cursor. (same as
"nocursor")
arrow:n set -arrow to alternate n.
xfixes enable xfixes cursor shape mode.
noxfixes disable xfixes cursor shape mode.
alphacut:n set -alphacut to n.
alphafrac:f set -alphafrac to f.
alpharemove enable -alpharemove mode.
noalpharemove disable -alpharemove mode.
alphablend disable -noalphablend mode.
noalphablend enable -noalphablend mode.
cursorshape disable -nocursorshape mode.
nocursorshape enable -nocursorshape mode.
cursorpos disable -nocursorpos mode.
nocursorpos enable -nocursorpos mode.
xwarp enable -xwarppointer mode.
noxwarp disable -xwarppointer mode.
buttonmap:str set -buttonmap "str", empty to disable
dragging disable -nodragging mode.
nodragging enable -nodragging mode.
wireframe enable -wireframe mode. same as "wf"
nowireframe disable -wireframe mode. same as "nowf"
wireframe:str enable -wireframe mode string.
wireframe_mode:str enable -wireframe mode string.
wirecopyrect:str set -wirecopyrect string. same as "wcr:
"
scrollcopyrect:str set -scrollcopyrect string. same "scr
"
noscrollcopyrect disable -scrollcopyrect mode. "noscr"
scr_area:n set -scr_area to n
scr_skip:list set -scr_skip to "list"
scr_inc:list set -scr_inc to "list"
scr_keys:list set -scr_keys to "list"
scr_term:list set -scr_term to "list"
scr_parms:str set -scr_parms parameters.
pointer_mode:n set -pointer_mode to n. same as "pm"
input_skip:n set -input_skip to n.
speeds:str set -speeds to str.
debug_pointer enable -debug_pointer, same as "dp"
nodebug_pointer disable -debug_pointer, same as "nodp"
debug_keyboard enable -debug_keyboard, same as "dk"
nodebug_keyboard disable -debug_keyboard, same as "nodk"
defer:n set -defer to n ms,same as deferupdate:n
wait:n set -wait to n ms.
wait_ui:f set -wait_ui factor to f.
wait_bog disable -nowait_bog mode.
nowait_bog enable -nowait_bog mode.
readtimeout:n set read timeout to n seconds.
nap enable -nap mode.
nonap disable -nap mode.
sb:n set -sb to n s, same as screen_blank:n
xdamage enable xdamage polling hints.
noxdamage disable xdamage polling hints.
xd_area:A set -xd_area max pixel area to "A"
xd_mem:f set -xd_mem remembrance to "f"
fs:frac set -fs fraction to "frac", e.g. 0.5
gaps:n set -gaps to n.
grow:n set -grow to n.
fuzz:n set -fuzz to n.
snapfb enable -snapfb mode.
nosnapfb disable -snapfb mode.
rawfb:str set -rawfb mode to "str".
progressive:n set libvncserver -progressive slice
height parameter to n.
desktop:str set -desktop name to str for new clients
.
rfbport:n set -rfbport to n.
httpport:n set -httpport to n.
httpdir:dir set -httpdir to dir (and enable http).
enablehttpproxy enable -enablehttpproxy mode.
noenablehttpproxy disable -enablehttpproxy mode.
alwaysshared enable -alwaysshared mode.
noalwaysshared disable -alwaysshared mode.
(may interfere with other options)
nevershared enable -nevershared mode.
nonevershared disable -nevershared mode.
(may interfere with other options)
dontdisconnect enable -dontdisconnect mode.
nodontdisconnect disable -dontdisconnect mode.
(may interfere with other options)
debug_xevents enable debugging X events.
nodebug_xevents disable debugging X events.
debug_xdamage enable debugging X DAMAGE mechanism.
nodebug_xdamage disable debugging X DAMAGE mechanism.
debug_wireframe enable debugging wireframe mechanism.
nodebug_wireframe disable debugging wireframe mechanism.
debug_scroll enable debugging scrollcopy mechanism.
nodebug_scroll disable debugging scrollcopy mechanism.
debug_tiles enable -debug_tiles
nodebug_tiles disable -debug_tiles
dbg enable -dbg crash shell
nodbg disable -dbg crash shell
noremote disable the -remote command processing,
it cannot be turned back on.
The vncconnect(1) command from standard VNC
distributions may also be used if string is prefixed
with "cmd=" E.g. 'vncconnect cmd=stop'. Under some
circumstances xprop(1) can used if it supports -set
(see the FAQ).
If "-connect /path/to/file" has been supplied to the
running x11vnc server then that file can be used as a
communication channel (this is the only way to remote
control one of many x11vnc's polling the same X display)
Simply run: 'x11vnc -connect /path/to/file -remote ...'
or you can directly write to the file via something
like: "echo cmd=stop > /path/to/file", etc.
-query variable Like -remote, except just query the value of
"variable". "-Q" is an alias for "-query".
Multiple queries can be done by separating variables
by commas, e.g. -query var1,var2. The results come
back in the form ans=var1:value1,ans=var2:value2,...
to the standard output. If a variable is read-only,
it comes back with prefix "aro=" instead of "ans=".
Some -remote commands are pure actions that do not make
sense as variables, e.g. "stop" or "disconnect",
in these cases the value returned is "N/A". To direct
a query straight to the VNC_CONNECT property or connect
file use "qry=..." instead of "cmd=..."
Here is the current list of "variables" that can
be supplied to the -query command. This includes the
"N/A" ones that return no useful info. For variables
names that do not correspond to an x11vnc option or
remote command, we hope the name makes it obvious what
the returned value corresponds to (hint: the ext_*
variables correspond to the presence of X extensions):
ans= stop quit exit shutdown ping blacken zero
refresh reset close disconnect id sid waitmapped
nowaitmapped clip flashcmap noflashcmap shiftcmap
truecolor notruecolor overlay nooverlay overlay_cursor
overlay_yescursor nooverlay_nocursor nooverlay_cursor
nooverlay_yescursor overlay_nocursor visual scale
scale_cursor viewonly noviewonly shared noshared
forever noforever once timeout deny lock nodeny unlock
connect allowonce allow localhost nolocalhost listen
lookup nolookup accept gone shm noshm flipbyteorder
noflipbyteorder onetile noonetile solid_color solid
nosolid blackout xinerama noxinerama xtrap noxtrap
xrandr noxrandr xrandr_mode padgeom quiet q noquiet
modtweak nomodtweak xkb noxkb skip_keycodes skip_dups
noskip_dups add_keysyms noadd_keysyms clear_mods
noclear_mods clear_keys noclear_keys remap repeat
norepeat fb nofb bell nobell sel nosel primary noprimary
cursorshape nocursorshape cursorpos nocursorpos cursor
show_cursor noshow_cursor nocursor arrow xfixes noxfixes
xdamage noxdamage xd_area xd_mem alphacut alphafrac
alpharemove noalpharemove alphablend noalphablend
xwarppointer xwarp noxwarppointer noxwarp buttonmap
dragging nodragging wireframe_mode wireframe wf
nowireframe nowf wirecopyrect wcr nowirecopyrect nowcr
scr_area scr_skip scr_inc scr_keys scr_term scr_parms
scrollcopyrect scr noscrollcopyrect noscr pointer_mode
pm input_skip input client_input speeds debug_pointer dp
nodebug_pointer nodp debug_keyboard dk nodebug_keyboard
nodk deferupdate defer wait_ui wait_bog nowait_bog wait
readtimeout nap nonap sb screen_blank fs gaps grow fuzz
snapfb nosnapfb rawfb progressive rfbport http nohttp
httpport httpdir enablehttpproxy noenablehttpproxy
alwaysshared noalwaysshared nevershared noalwaysshared
dontdisconnect nodontdisconnect desktop debug_xevents
nodebug_xevents debug_xevents debug_xdamage
nodebug_xdamage debug_xdamage debug_wireframe
nodebug_wireframe debug_wireframe debug_scroll
nodebug_scroll debug_scroll debug_tiles dbt
nodebug_tiles nodbt debug_tiles dbg nodbg noremote
aro= display vncdisplay desktopname http_url auth
users rootshift clipshift scale_str scaled_x scaled_y
scale_numer scale_denom scale_fac scaling_blend
scaling_nomult4 scaling_pad scaling_interpolate inetd
privremote unsafe safer nocmds passwdfile using_shm
logfile o flag rc norc h help V version lastmod bg
sigpipe threads readrate netrate netlatency pipeinput
clients client_count pid ext_xtest ext_xtrap ext_xrecord
ext_xkb ext_xshm ext_xinerama ext_overlay ext_xfixes
ext_xdamage ext_xrandr rootwin num_buttons button_mask
mouse_x mouse_y bpp depth indexed_color dpy_x dpy_y
wdpy_x wdpy_y off_x off_y cdpy_x cdpy_y coff_x coff_y
rfbauth passwd
-sync By default -remote commands are run asynchronously, that
is, the request is posted and the program immediately
exits. Use -sync to have the program wait for an
acknowledgement from the x11vnc server that command was
processed (somehow). On the other hand -query requests
are always processed synchronously because they have
to wait for the result.
Also note that if both -remote and -query requests are
supplied on the command line, the -remote is processed
first (synchronously: no need for -sync), and then
the -query request is processed in the normal way.
This allows for a reliable way to see if the -remote
command was processed by querying for any new settings.
Note however that there is timeout of a few seconds so
if the x11vnc takes longer than that to process the
requests the requestor will think that a failure has
taken place.
-noremote Do not process any remote control commands or queries.
-yesremote Do process remote control commands or queries.
Default: -yesremote
A note about security wrt remote control commands.
If someone can connect to the X display and change
the property VNC_CONNECT, then they can remotely
control x11vnc. Normally access to the X display is
protected. Note that if they can modify VNC_CONNECT
on the X server, they have enough permissions to also
run their own x11vnc and thus have complete control
of the desktop. If the "-connect /path/to/file"
channel is being used, obviously anyone who can write
to /path/to/file can remotely control x11vnc. So be
sure to protect the X display and that file's write
permissions. See -privremote below.
If you are paranoid and do not think -noremote is
enough, to disable the VNC_CONNECT property channel
completely use -novncconnect, or use the -safer
option that shuts many things off.
-unsafe A few remote commands are disabled by default
(currently: id:pick, accept:<cmd>, gone:<cmd>, and
rawfb:setup:<cmd>) because they are associated with
running external programs. If you specify -unsafe, then
these remote-control commands are allowed. Note that
you can still specify these parameters on the command
line, they just cannot be changed via remote-control.
-safer Equivalent to: -novncconnect -noremote and prohibiting
-gui and the -connect file. Shuts off communcation
channels.
-privremote Perform some sanity checks and disable remote-control
commands if it appears that the X DISPLAY and/or
connectfile can be accessed by other users. Once
remote-control is disabled it cannot be turned back on.
-nocmds No external commands (e.g. system(3), popen(3), exec(3))
will be run.
-deny_all For use with -remote nodeny: start out denying all
incoming clients until "-remote nodeny" is used to
let them in.
These options are passed to libvncserver:
-rfbport port TCP port for RFB protocol
-rfbwait time max time in ms to wait for RFB client
-rfbauth passwd-file use authentication on RFB protocol
(use 'storepasswd' to create a password file)
-passwd plain-password use authentication
(use plain-password as password, USE AT YOUR RISK)
-deferupdate time time in ms to defer updates (default 40)
-desktop name VNC desktop name (default "LibVNCServer")
-alwaysshared always treat new clients as shared
-nevershared never treat new clients as shared
-dontdisconnect don't disconnect existing clients when a new non-shared
connection comes in (refuse new connection instead)
-httpdir dir-path enable http server using dir-path home
-httpport portnum use portnum for http connection
-enablehttpproxy enable http proxy support
-progressive height enable progressive updating for slow links
-listen ipaddr listen for connections only on network interface with
addr ipaddr. '-listen localhost' and hostname work too.
Pretty wild huh? [1]Contact me if you have any questions or problems.
Personally, I use:
x11vnc -rfbauth $HOME/.vnc/passwd -flashcmap -cursor X -solid
(the -flashcmap only matters on old 8-bit X displays)
References
1. mailto:xvml@karlrunge.com
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