A Linux User Reference

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KDE Display Manager

  • KDM startup
    • On start up reads its configuration from the folder $KDEDIR/share/config/kdm/ (or /etc/kde4/kdm/ - could vary).
    • The main configuration file is $KDEDIR/kdmrc. All other files are referenced from this file and therefore could be stored under any name anywhere on the system.

    'kdm' is usually added to /etc/inittab.

    kdm inittab entry


    or if no inittab (as in ubuntu and ubuntu based distros) ..

    Set as default display manager - /etc/X11/default-display-manager


    For FreeBSD

    Find the line like /etc/ttys in /etc/inittab

    ttyv8   "/usr/X11R6/bin/xdm -nodaemon"  xterm off secure

    and change to something like

    ttyv8   "/opt/kde/bin/kdm"  xterm on secure

    Most other distributions will be a variation of one of these. The runlevel for X varies on distributions e.g. Ubuntu is 2.

    Basically, the X server starts, then it looks to see which display manager it should run.

    Test it - /sbin/init

    # /sbin/init 5

    On ubuntu use 2 instead of 5.

    Boot to multi-user X window envirmonment - /etc/inittab


    On ubuntu use 2 instead of 5. On reboot should end up with the graphical kdm login dialog.

  • KDM main configuration file

    kdm (comes with the KDE desktop) is a replacement of xdm and configures the same way, except that the location of its files vary:

    • /etc/X11/kdm in Caldera/SCO
    • /etc/kde/kdm in Red Hat (and Fedora Core)
    • /usr/share/config/kdm in Mandrake - a symbolic link to /etc/kde/kdm

    The kdm master configuration file

    • a '.ini' like file
    • it's options are key/value pairs (word boundaries), placed in [sections]
    • everything in the file is case sensitive
    • syntax errors and unrecognised key/section identifiers cause kdm to issue non-fatal error messages
    File format

    Lines beginning with # are comments, empty lines are ignored

    Can configure every X-display individually
    Every display has a display name, which consists of a host name (empty for local displays specified in StaticServers or ReserveServers), a colon and a display number. A display also belongs to a display class (which can be ignored in most cases)

    Sections with display-specific settings have the formal syntax [X-host[:number[_ class]]-sub-section] Common sections are:

      [X-*]  (all displays)
      [X-:*] (all local displays)
      [X-:0] (the first local display)
    [Section] Key Default Description
    [General] Global options that do not fit into any specific section
    StaticServers :0 List of displays (X-Servers) permanently managed by kdm. Displays with a hostname are foreign displays
    [X-*-Core] Options concerning the configuration of the kdm backend
    ServerAttempts 1 Number of attempts to start up a local X-Server. Starting up includes executing it and waiting for it to come up.
    ServerTimeout 15 Number of seconds kdm should wait for a local X-Server to come up
    ServerCmd /usr/X11R6/bin/X The command line to start the X-Server, without display number and VT spec.
    ServerArgs Local Additional arguments for the X-Servers for local sessions
    ServerArgs Remote Additional arguments for the X-Servers for remote sessions
    Setup Program to run (as root) before greeter window. May be used to change the appearance of the screen around the greeter window or to put up other windows. Conventionally called Xsetup.
    Startup Program to run (as root) after successful user authentication. Conventional name for a file used here is Xstartup
    Session ${x_bindir}/xterm -ls -T Program to run for the session
    FailsafeClient ${x_bindir}/xterm If the Session program fails to execute, kdm will fall back to this program. No args. but same environment variables as Session
    AllowRootLogin true If disabled - true, do not allow root (and any other user with UID = 0) to log in directly
    SessionsDirs ${kde_datadir}/kdm/sessions A list of directories containing session type definitions
    [Xdmcp] Options that control kdm's handling of XDMCP requests
    Enable true Whether kdm should listen to incoming XDMCP requests
    Port 177 UDP port number which kdm uses to listen for incoming XDMCP requests
    Xaccess ${kde_confdir}/kdm/Xaccess Prevent unauthorized XDMCP service and to allow forwarding of XDMCP IndirectQuery requests - hosts list
    [X-*-Greeter] Options concerning the configuration of the kdm frontend (greeter)
    UseBackground true If enabled, kdm will automatically start the krootimage program to set up the background
    BackgroundCfg ${kde_confdir}/kdm/backgroundrc Configuration file to be used by krootimage. It contains a section named [Desktop0] like kdesktoprc does
    GreeterPos 50,50 The relative coordinates (percentages of the screen size; X,Y) at which the centre of the greeter is put
    GreetString The headline in the greeter. An empty greeting means none at all
    Chooser Hosts* A list of hosts to be automatically added to the remote login menu. The special name * means broadcast
    X access control

    The file specified by the [xdmcp] Xaccess option provides information which kdm uses to control access from displays requesting service via XDMCP.

    The file contains four types of entries:

    • entries which control the response to Direct and Broadcast queries
    • entries which control the response to Indirect queries
    • macro definitions
    • entries which control on which network interfaces kdm listens for XDMCP queries

    The last entry type is the LISTEN directive. The formal syntax is: LISTEN [interface [multicast list]]

    • if one or more LISTEN lines are specified, kdm listens for XDMCP requests only on the specified interfaces
    • may be a hostname or IP address or the wildcard * to represent all available network interfaces
    • if multicast group addresses are listed on a LISTEN line, kdm joins the multicast groups on the given interface
    Setup program

    The Xsetup program is run after the X-Server is started or reset, but before the greeter is offered.

    This is the place to change the root background (if UseBackground is disabled) or bring up other windows that should appear on the screen along with the greeter.

    Startup program

    The Xstartup program is run as root when the user logs in.

    This is the place to put commands which add entries to utmp (the sessreg program may be useful here), mount users' home directories from file servers or abort the session if some requirements are not met (but note that on modern systems, many of these tasks are already taken care of by PAM modules).

    Session program

    The Xsession program is the command which is run as the user's session.

    It is run with the permissions of the authorized user. One of the keywords failsafe, default or custom or a string to eval by a Bourne-compatible shell is passed as the first argument.

  • Setup the automatic starting of X on all displays
    ServerCmd /usr/X11R6/bin/X
  • Add a greeting on all displays
    GreetString "Hi there"
  • Change colour depth for all displays
    ServerArgsLocal -bpp 16
  • Enable xdmcp on xserver
    Enable true