Created Tuesday 2006-08-22

1. Restarting GDM

GDM is the most common X display manager for the linux distributions. It's very similar to XDM, and the GDM instance is used to manage several virtual terminals, both text and X. If GDM dies then the instance can be restarted with:

        ctrl+alt+backpace

Otherwise, to restart GDM, open a virtual console (e.g., ctrl+alt+F1) and grep for the gdm(1) instance:

        bash# ps -elf| egrep gdm | egrep -v grep

Once you have the gdm pid, send a SIGHUP (signal #1) to the process. This needs to be done as root or as the user that owns the process:

        bash# kill -1 29999

2. Starting multiple displays under GDM

By default, GDM starts a single virtual X session on :0, which is accessed via ctrl+alt+F7. There are 6 virtual consoles (text) started as well, these are ctrl+alt+F1 through ctrl+alt+F6.

To start more than one virtual X terminal session, e.g., display :1 accessed with ctrl+alt+F8, display :2 accessed with ctrl+alt+F9 and etc, edit your gdm(1) configuration, which is typically in /etc/X11/gdm/gdm.conf, and set the following options:

Note gdm.conf locations:
FC4: /etc/X11/gdm/gdm.conf
FC5: /usr/share/gdm/defaults.conf

    [daemon]
    FlexibleXServers=5  # Not completely sure that this one is 
                        # related, but it "soundes" like it is.
                        # 5 is the default on my debian install anyway.

    FirstVT=7           # This would be correct on a "traditional" distro 
                        # install, adjust for yours
    VTAllocation=true

    [servers]
    0=Standard          # This is F7 in our "traditional" setup
    1=Standard          # Now we've got a second x session, this one's on F8
    2=Standard          # No. 3, it's on f9, and so on.

    Next restart gdm(1) and that's it.

        bash# gdm-safe-restart

3. GDM Theme Tester

GDM is supplied with a shell script which is useful in testing GDM themes. It starts an Xnest session with the named theme. This script can run in non-priviledged mode, but requires that the X11 library for Xnest is installed. E.g., to test the theme "mono-metal"

bash$ gdmthemetester flexi mono-metal

    The second argument is called the "environment" and supported values are
    "console", "flexi", "flexi-remote", "console-timed" and "xdmcp".

4. Start new nested GDM Login

    It's possible to launch new gdm login sessions within the current session
    by using the GDM Flexiserver with the Xnest option. These nested
    subsessions can be started as a non-priviledged user. Note, the X11 
    Xnest libaries must be installed.

        bash$ gdmflexiserver  --xnest

    By default, the flexiserver will start the new gdm login manager within
    an Xnest server window that is 3/4 of the size of the root window. This
    behaviour can be changed by specifying a (standard X11) geometry or by
    setting the XNESTSIZE variable.