This info is based on my RedHat 6.1 default KDE Workstation installation. If you are using another distribution, or even another version of RedHat, or a different Workstation install, then you may have to do some detective work. Hopefully, this info will give you what you need to start detecting! This HOWTO began as the result of wondering how to add another window manager or desktop environment to the drop-down list on the GUI login screen; further investigation revealed other configuration options.
I began my own "detective work" when I found a reference on a RedHat List which
/etc/inittab, and its role in system startup. In
/etc/inittab I found the following entries, which define how the
X Window System is started in my distribution and version:
# Run xdm in runlevel 5 # xdm is now a separate service x:5:respawn:/etc/X11/prefdm -nodaemon
Here is what prefdm looks like:
#!/bin/sh PATH=/sbin:/usr/sbin:/bin:/usr/bin:/usr/X11R6/bin # Run preferred X display manager preferred= if [ -f /etc/sysconfig/desktop ]; then if grep -q GNOME /etc/sysconfig/desktop 2>/dev/null; then preferred=gdm elif grep -q KDE /etc/sysconfig/desktop 2> /dev/null; then preferred=kdm elif grep -q AnotherLevel /etc/sysconfig/desktop 2> /dev/null; then preferred=xdm fi fi if [ -z ":$preferred" ]; then if which gdm >/dev/null 2>&1; then preferred=gdm elif which kdm >/dev/null 2>&1; then preferred=kdm elif which xdm >/dev/null 2>&1; then preferred=xdm fi fi if [ -n "$preferred" ] && which $preferred >/dev/null 2>&1; then exec `which $preferred` $* fi exit 1
No changes to prefdm are necessary; it determines which display manager is the
system default, and which runs the GUI login. During boot-up, prefdm parses
/etc/sysconfig/desktop and selects the display manager listed there;
in the case of my KDE Workstation install, this is kdm (KDE Display Manager).
Note that gdm (Gnome Display Manager) is not installed on my system; xdm (X
Display Manager) is installed by default as part of the X Window System, and
was apparently used by older versions of Red Hat.