Forcing IceWM as the default under GDM in Fedora

From K12LTSP Wiki

Instructions to make IceWM the default under GDM in Fedora:

Updated instructions for Fedora Core 6 (Zod) / K12LTSP release 6.0.0-2
this script worked on a fresh install, to make IceWM the only login choice.
-- Patrick Healy, Palm Desert High School

#! /bin/bash
cd /etc/X11/dm/Sessions
mkdir disabled
mv Reset.desktop disabled
cd /etc/X11/gdm/Sessions
mkdir disabled
mv Reset\ your\ desktop disabled/
cd /usr/share/gdm/BuiltInSessions
mkdir disabled
mv default.desktop disabled/
cd /usr/share/xsessions/
mkdir disabled
mv gnome.desktop disabled/
mv kde.desktop disabled/
mv reset.desktop disabled/
# this next command will make a duplicate icewm session login choice, 
# but it does force icewm as the default
cp -a /usr/share/xsessions/icewm.desktop /usr/share/gdm/BuiltInSessions/default.desktop
# now clean up the extra copy of icewm session login choice
mv icewm.desktop disabled/

Here's some interesting background information
(not necessary for the above to work)

from /usr/share/gdm/defaults.conf
(used to be /etc/X11/gdm/gdm.conf)

# GDM Configuration file.
#
# This file should not be updated by hand.  Since GDM 2.13.0.4,
# configuration choices in the /etc/X11/gdm/gdm.conf-custom file will
# override the default values specified in this file (installation 
# locations of the configuration files may vary for different distros).
# This defaults.conf file may be overwritten on upgrade, so to ensure
# that your configuration choices are not lost, please make sure that 
# your changes are made only the the custom.conf file.
#
# If you were using an older version of GDM, your system may have the
# the older gdm.conf configuration file on the system.  If so, then this
# file is used instead of the custom.conf file for backwards support.
# If you make changes to the custom.conf file and they seem to not be
# taking effect, this is likely the problem.  Consider migrating your
# configuration to the new custom.conf file and removing the gdm.conf
# file.
=================================================
I suspect the custom file referred to is really located here now:
/etc/gdm/custom.conf
=================================================

Here's the original instructions (Feb 2004):

First, edit gdm.conf (located in /etc/X11/gdm/)
and change line #109 from:
~DefaultSession=default.desktop
to:
~DefaultSession=IceWM.desktop
now, restart gdm (lots of ways, including rebooting the server).

Next, create a subdirectory called "disabled" in each of two locations listed on line #107 of gdm.conf as the "~SessionDesktopDir", and move any "*.desktop" session files you don't want into "disabled", including the original default one. (This approach is reversible, unlike just deleting the files).

Example:

# cd /etc/X11/dm/Sessions
# mkdir disabled
# mv default.desktop disabled
# mv gnome.desktop disabled
# cd /usr/share/xsessions
# mkdir disabled
# mv gnome.desktop disabled
# mv kde.desktop disabled

On their next restart, the clients will boot to IceWM with no other choices available, except resetting their desktop, and failsafe mode.