tdebase/kdm

This is the K Display Manager (KDM) for KDE 3.4,
the KDE replacement for the X Display Manager (XDM).

Semi-official home page: http://devel-home.kde.org/~ossi/sw/kdm.html


configure options that affect KDM
---------------------------------

--with-pam[=service]
  Compile KDM (and other parts of kdebase) with PAM support. The default
  service is "kde". PAM is automatically used if found.

--with-kdm-pam=service
  Override the PAM service used specifically by KDM. Depends on --with-pam.

--with-shadow
  Compile KDM (and other parts of kdebase) with shadow password support.
  Shadow passwords are automatically used if found. This affects KDM only
  if PAM is not used.

--with-krb4[=path]
  Compile KDM (and the LDAP KIO slave) with KTH Kerberos 4 support. Note
  that this does not work with the Kerberos 4 compatibility layer found in
  MIT Kerberos 5. This affects KDM only if PAM is not used.

--with-afs
  Compile KDM with AFS support. Depends on --with-krb4.

--with-krb5auth[=path]
--with-rpcauth
  Compile KDM with Kerberos 5 resp. secure RPC support for X authorization
  cookies. It's pretty pointless to enable this if you don't use an X server
  that supports it.
  
  If you want user authentication against a Kerberos realm, compile KDM with
  PAM support and use the appropriate module.

--without-xdmcp
  Compile KDM without XDMCP support.

--with-kdm-xconsole
  Compile KDM with a builtin "xconsole" replacement in the greeter. I don't
  consider this too useful, but SuSE wanted it, so it's there. ;)


KDM's file system layout
------------------------

${kde_confdir} is usually ${prefix}/share/config
${kde_datadir} is usually ${prefix}/share/apps
The indented locations are envisioned for a configuration shared with GDM.

${kde_confdir}/kdm/{kdmrc,Xservers,Xaccess,Xwilling,...}
${kde_datadir}/kdm/sessions/*.desktop
  /etc/X11/sessions/,/usr/share/xsessions/
${kde_datadir}/kdm/pics/users/
${kde_datadir}/kdm/pics/
${kde_datadir}/kdm/faces/*.face{,.icon}
  /usr/share/faces/
/var/run/xauth/A*
/var/run/xdmctl/xdmctl*
/var/run/kdm.pid
/var/lib/kdm/kdmsts
<site-specific>/*.dmrc
$HOME/.face{,.icon}
$HOME/.dmrc


How to setup KDM
----------------

KDM's config files are all located in ${kde_confdir}/kdm.
"make install" will create a probably working configuration, either by
deriving it from an already present KDM/XDM installation or by using
defaults if no previous installation is found.

You can change the configuration from the KDE Control Center. You will
find the "Login Manager" module in the "System Administration" group.

Have a look at README.pam in the kdebase top level directory if your
system uses PAM.


Configuring session types
-------------------------

The way session types are configured changed drastically in KDE 3.2.
Session types are now represented by .desktop files in appropriate locations.
The format of the .desktop files is (not yet) defined in the FreeDesktop.org
desktop entry spec. Differences to "standard" .desktop files are:
- the Type is fixed to XSession and can be omitted
- the Encoding is fixed to UTF-8 and can be omitted
- the Exec field will be passed to "eval exec" in a bourne shell; no macro
  expansion is performed on it. "default", "custom" and "failsafe" are magic
  constants that cause special actions.
- Name, Comment, TryExec and Hidden are supported
- the remaining keys have no meaning currently
Session types are internally identified by filename (without extension);
that's what will be saved to ~/.dmrc and what DESKTOP_SESSION will be set to.
For every magic Exec constant a session type of the same name exists.

Unless your system is configured differently already, you should create a
directory ${kde_confdir}/kdm/sessions and add this to kdmrc:

[X-*-Core]
SessionsDirs=${kde_confdir}/kdm/sessions,${kde_datadir}/kdm/sessions

(Note that you must use actual paths instead of variables, see the section
about KDM's file system layout.)
Do any changes only in the config directory - any changes in the data
directory will be lost after the next KDE update.

To override a session type, copy the .desktop file from the data dir to the
config dir and edit it at will. Removing the shipped session types can be
accomplished by "shadowing" them with .desktop files containing Hidden=true.
For the magic session types no .desktop files exist by default, but KDM
pretends they would, so you can override them like any other type.
I guess you already know how to add a new session type by now. ;-)


Running KDM from init
---------------------

NOTE, that this description applies to RedHat 5.x and must be adapted for
other distributions/systems. Generally I'd advise _against_ starting KDM
directly from init - better use a proper init script, possibly by slightly
modifying the XDM init script shipped by your distribution.

   Edit (as root) /etc/inittab.

   Look for the line:

       x:5:respawn:/usr/X11/bin/xdm -nodaemon

   Replace it with:

       x:5:respawn:/opt/kde/bin/kdm

   This tells init(8) to respawn KDM, the KDE display manager, when
   the system is in run level 5.
   Note that KDM does not need the -nodaemon option.

   To start KDM, either run (as root) /sbin/telinit 5 (to switch to
   run level 5), or (this is risky! don't do it until you _know_ you
   want the system to boot into this every time!) edit /etc/inittab
   and change the line:

       id:3:initdefault:

   to

       id:5:initdefault:

   If you do the latter step, then every time your system boots
   successfully it will go into run level 5 and run KDM,
   presenting you the exceedingly cute KDE login screen.


The command sockets
-------------------

This is a feature you can use to remote-control KDM. It's mostly intended
for use by ksmserver and kdesktop from a running session, but other
applications are possible as well.

The sockets are UNIX domain sockets which live in subdirectories of the
directory specified by FifoDir=. The subdir is the key to addressing and
security; the sockets all have the file name "socket" and file permissions
rw-rw-rw- (0666). This is because some systems don't care for the file
permissions of the socket files.
There are two types of sockets: the global one (dmctl) and the per-display
ones (dmctl-<display>).
The global one's subdir is owned by root, the subdirs of the per-display
ones' are owned by the user currently owning the session (root or the
logged in user). Group ownership of the subdirs can be set via FifoGroup=,
otherwise it's root. The file permissions of the subdirs are rwxr-x--- (0750).

The fields of a command are separated by tabs (\t), the fields of a list
are separated by spaces, literal spaces in list fields are denoted by "\s".
The command is terminated by a newline (\n).
The same applies to replies. The reply on success is "ok", possibly followed
by the requested information. The reply on error is an errno-style word (e.g.,
"perm", "noent", etc.) followed by a longer explanation.

Global commands:

"login" display ("now"|"schedule") user password [session_arguments]
 - login user at specified display. if "now" is specified, a possibly
   running session is killed, otherwise the login is done after the
   session exits.
   session_arguments are printf-like escaped contents for .dmrc. Unlisted
   keys will default to previously saved values.

Per-display commands:

"lock"
 - The display is marked as locked. If the X-Server crashes in this state,
   no auto-relogin will be performed even if the option is on.

"unlock"
 - Reverse the effect of "lock": re-enable auto-relogin.

"suicide"
 - The currently running session is forcibly terminated. No auto-relogin is
   attempted, but a scheduled "login" command will be executed.

Commands for all sockets:

"caps"
 - Returns a list this socket's capabilities:
   "kdm" - identifies kdm, in case some other DM implements this protocol, too.
   "list", "activate", "lock", "suicide", "login" - the respective command
     is supported.
   "bootoptions" - the "listbootoptions" command and the "=" option to
     "shutdown" are supported.
   "shutdown <list>" - "shutdown" is supported and allowed to the listed users
     (comma-separated). "*" means all authenticated users.
   "shutdown" - "shutdown" is supported and allowed to everybody.
   "nuke <list>" - forced shutdown is allowed to the listed users.
   "nuke" - forced shutdown is allowed to everybody.
   "reserve <number>" - reserve displays are configured and <number> are
     available at this time.

"list" ["all"|"alllocal"]
 - Return a list of running sessions. By default all active sessions are
   listed. If "all" is specified, passive sessions are listed as well. If
   "alllocal" is specified, passive sessions are listed as well, but all
   incoming remote sessions are skipped.
   Each session entry is a comma-separated tuple of:
   - Display or TTY name
   - VT name for local sessions
   - Logged in user's name, empty for passive sessions and outgoing remote
     sessions (local chooser mode)
   - Session type or remote host for outgoing remote sessions, empty for
     passive sessions
   - A flag field:
     - "t" for tty sessions
     - "*" for the display belonging to the requesting socket
     - "!" for sessions that cannot be killed by the requesting socket
     - New flags might be added later
   - New fields might be added later

"reserve" [timeout in seconds]
 - Start a reserve login screen. If nobody logs in within the specified amount
   of time (one minute by default), the display is removed again. When the
   session on the display exits, the display is removed, too.
 - Permitted only on sockets of local displays and the global socket.

"activate" (vt|display)
 - Switch to a particular VT (virtual terminal). The VT may be specified
   either directly (e.g., vt3) or by a display using it (e.g., :2).
 - Permitted only on sockets of local displays and the global socket.

"listbootoptions"
 - List available boot options.
 => "ok" list default current
    default and current are indices into the list and are -1 if unset or
    undeterminable.

"shutdown" ("reboot"|"halt") ["="bootchoice] \
  ("ask"|"trynow"|"forcenow"|"schedule"|\
   start ("-1"|end ("force"|"forcemy"|"cancel")))
 - Request a system shutdown, either a reboot or a halt/poweroff.
 - An OS choice for the next boot may be specified from the list returned by
   "listbootoptions".
 - Shutdowns requested from per-display sockets are executed when the current
   session on that display exits. Such a request may pop up a dialog asking
   for confirmation and/or authentication.
 - start is the time for which the shutdown is scheduled. If it starts with
   a plus-sign, the current time is added. Zero means immediately.
 - end is the latest time at which the shutdown should be performed if active
   sessions are still running. If it starts with a plus-sign, the start time
   is added. Minus one means wait infinitely. If end is through and active
   sessions are still running, KDM can do one of the following:
   * "cancel" - give up the shutdown.
   * "force" - shut down nonetheless.
   * "forcemy" - shut down nonetheless if all active sessions belong to the
                 requesting user. Only for per-display sockets.
 - start and end are specified in seconds since the UNIX epoch.
 - "trynow" is a synonym for "0 0 cancel", "forcenow" for "0 0 force" and
   "schedule" for "0 -1".
 - "ask" attempts an immediate shutdown and interacts with the user if active
    sessions are still running. Only for per-display sockets.

"shutdown" "cancel" ["local"|"global"]
 - Cancel a scheduled shutdown. The global socket always cancels the currently
   pending shutdown, while per-display sockets default to cancelling their
   queued request.

"shutdown" "status"
 - Return a list with information about shutdowns.
   The entries are comma-separated tuples of:
   - ("global"|"local") - pending vs. queued shutdown. A local entry can be
     returned only by a per-display socket.
   - ("halt"|"reboot")
   - start
   - end
   - ("ask"|"force"|"forcemy"|"cancel")
   - Numeric user ID of the requesting user, -1 for the global socket.
   - The next boot OS choice or "-" for none.
   - New fields might be added later.
 
There are two ways of using the sockets:
- Connecting them directly. FifoDir is exported as $DM_CONTROL; the name
  of per-display sockets can be derived from $DISPLAY.
- By using the kdmctl command (e.g., from within a shell script).
  Try "kdmctl -h" to find out more.

Here is an example bash script "reboot into FreeBSD":

if kdmctl | grep -q shutdown; then
  IFS=$'\t'
  set -- `kdmctl listbootoptions`
  if [ "$1" = ok ]; then
    fbsd=$(echo "$2" | tr ' ' '\n' | sed -ne 's,\\s, ,g;/freebsd/I{p;q}')
    if [ -n "$fbsd" ]; then
      kdmctl shutdown reboot "=$fbsd" ask > /dev/null
    else
      echo "FreeBSD boot unavailable."
    fi
  else
    echo "Boot options unavailable."
  fi
else
  echo "Cannot reboot system."
fi


"It doesn't work!!"
-------------------

More input! ;-)

KDM accepts two command line options related to logging:

  -debug <n>
    <n> is a decimal or hexadecimal (prefix 0x) number.
    The number is a bitfield, i.e., it is formed by summing up the
    required values from this table:
    1 (0x1) - core debugging. Probably the most useful one.
    2 (0x2) - config reader debugging.
    4 (0x4) - greeter debugging.
    8 (0x8) - IPC debugging. This logs _all_ communication between the
	      core, the config reader and the greeter - including the
	      passwords you type, so edit the log before showing it to
	      somebody.
	      This attempts to synchronize the processes to interleave the
	      log messages optimally, but will probably fail unless you use
	      -debug 0x80 as well.
    16 (0x10) - wait after forking session sub-daemon.
    32 (0x20) - wait after starting config reader.
    64 (0x40) - wait after starting greeter.
	The wait options are only useful if you need to attach a debugger
	to a process, but it crashes before you are able to do so without
	the delay. See below.
    128 (0x80) - don't use syslog for internally generated messages.
    256 (0x100) - core Xauth debugging.
    1024 (0x400) - run config reader and greeter through valgrind.
    2048 (0x800) - run config reader and greeter through strace.

    Logs from "-debug 7" are usually a good start.

  -logfile <file>
    <file> is the file to log various messages to. The default log file is
    /var/log/kdm.log. For internal reasons there is no option in kdmrc to
    permanently specify the log file location. If you redirect KDM's
    standard error output to a file, KDM will log there.
    If KDM is configured to use syslog (and it _very_ probably is on any
    modern system), all internally generated messages are logged to the
    "daemon" facility. The log usually can be found in /var/log/debug.log
    and /var/log/daemon.log; make sure that daemon.* is logged (look at
    /etc/syslog.conf).
    If you have problems logging in and your system uses PAM (also quite
    probable on modern systems), the "auth" and "authpriv" syslog facilities
    are interesting, too.

Send me all the logs together with a detailed description of what you did
and what happened. If your problem is related to a specific configuration,
you should also attach a tar.gz archive of your KDM config directory.

If I request a backtrace from you and KDM didn't create one yet via the
usual drkonqi procedure, you'll have to do that yourself. The keyphrase
is "attaching gdb". How exactly this is done depends on the part that
crashes:
- master daemon. Actually you should never need to attach to it, as
  you can start it within the debugger already:
  # gdb --args kdm -nodaemon -debug 7
  (gdb) run
- display subdaemon. Find (using ps) the process with a name like
  "-:0" (where :0 is actually the display this process is for). This
  process' PPID is the master daemon. Attach to it this way:
  # gdb kdm <the PID you found>
  (gdb) cont
  If the subdaemon crashes before you can attach, add 16 to the debug flags
  when you start KDM.
- config reader. You will have to add 32 to the debug flags almost certainly.
  The PPID will be the master daemon as well.
  # gdb kdm_config $(pidof kdm_config)
  (gdb) cont
- greeter. If it's too fast, add 64 to -debug. The PPID will be the subdaemon.
  # gdb kdm_greet $(pidof kdm_greet)
  (gdb) cont
  The simplification with "pidof" works only if you have only one display,
  otherwise you have to find the PID manually (by using ps -fx).
Once you got gdb attached to the offending process, do whatever is needed
to make it crash (probably nothing, if you had to use a delay parameter).
Once it crashed, gdb will tell you a signal name, like SIGSEGV - that's the
first interesting part for me. Then you have to create the actual backtrace:
  (gdb) bt
The output of this command is interesting for me.
I might request a backtrace even if nothing crashes, but instead hangs. In
this case don't use "cont" after attaching, but use "bt" right away. If the
process is already running, interrupt it with ctrl-c.
For obvious reasons you have to run gdb on a different virtual terminal than
the X server. To get there, press alt-ctrl-f1 and log in as root. To
switch to the X server's vt, press alt-ctrl-f7 (the exact function key may
be different on your system). You may also use a remote login from a
second machine. In any case it is advantageous to have mouse support on the
debugging console for copying the backtrace.
Note that a backtrace is usually _much_ more useful if the binary contains
debugging info, so you should install from source with the --enable-debug
configure flag if at all possible.


Random rambings and license information
---------------------------------------

Version 0.1 of KDM is copyright
	Matthias Ettrich <ettrich@trolltech.com>
All later versions copyright:
	(C) 1997-2000 Steffen Hansen <hansen@kde.org>
Since version 0.90 (KDE 2.1) copyright:
	(C) 2000-2003 Oswald Buddenhagen <ossi@kde.org>

The files in the backend directory are licensed under the X licence
(see http://www.x.org/Downloads_terms.html for more info).
The files in the kfrontend directory are licensed under the GNU GPL.

Thanks to (in no particular order):
Michael Bach Jensen and Torsten Rahn for drawing icons.
Duncan Haldane for investigation of PAM issues.
Stephan Kulow for helping with the autoconf stuff.
Martin Baehr for intensive testing and writing the sample Xsession scripts.
Harald Hoyer <Harald.Hoyer@redhat.de> for the (now obsoleted) chooser.
SuSE for employing me (ossi) for three months to work on kdm.
BasysKom for sponsoring my (ossi's) work on the conversation plugin stuff.
... and _many_ others ...


-- 
Have fun with it (and feel free to comment),

	Oswald Buddenhagen <ossi@kde.org>