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Copyright (c) 2002 by John Meshkoff
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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
mentioned /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.
WARNING: The procedures explained in this HOWTO involve making changes to system configuration files; if you are not experienced in making such changes, some caution is required. Introducing errors into such files may make your system unstable, or cause it to crash. The procedures explained in this HOWTO have been tested and should not cause problems if used correctly.
If you have KDE 2.2 or higher, and you are not comfortable with manual editing of system files, you may open a terminal window (xterm or konsole) from your user desktop (NOT the root desktop), then type and enter:
su -c 'kcontrol'
Enter your root password at the prompt, and make the changes from within the KDE Control Center that appears: go to Applications ==> Login Manager. Choose the appropriate configuration tab; you can easily configure every aspect of the login screen from there. In Earlier versions of KDE, kcontrol can modify kdmrc, but cannot modify Xsession which is used in those versions; see the note below about changes from KDE 2.2 and higher.
To see how to manually configure some of these, and see what these configuration files do, proceed as follows:
(Caution: Some configuration files have changed since the version of kdm I'm using, particularly since KDE > 2.0:
The following is quoted from the FreeBSD Handbook-X11:
"Note: In KDE 2.2 this has changed: kdm now uses its own configuration files. Please see the KDE 2.2 documentation for details.")
Note: KDE 3.1 has added kdm documentation, see The kdm Handbook
Much of the material in this new handbook applies to the older versions; new features are also described therein.
Check the documentation for your version to identify the current configuration files if you want to manually edit these, or just want to see how they work.
Do not use a word-processor program for editing system configuration files; such programs introduce special formatting characters which will corrupt the files. Use a text-editor, particularly one which can handle long lines without introducing extra carriage-return or line feed characters into existing code. Suitable editors include vim (vi improved), vi, and emacs. There are others, but these are usually installed by default in Linux workstation installations; they each have features which make them especially suitable for writing and editing computer code. See the bibliography section at the end of this HOWTO for more information.
IMPORTANT: Before making changes to any system configuration files, you should make back-up copies of the originals, so you can restore them in case of serious errors!
The files which we will be changing here are /usr/share/config/kdmrc, which
is where we add selection labels to the drop-down list on the login screen, and
/etc/X11/xdm/Xsession, which is where we add the path to the executables
for our labels (if you are using a different distribution, the path to these
files may be different; just do "locate kdmrc" and "locate Xsession"
in the shell [i.e., in a terminal emulation, such as xterm, or KDE's konsole]
to find them).
The default line to change in kdmrc looks like this:
SessionTypes=kde;gnome;anotherlevel;default;failsafe;
After adding selection labels for two new window managers, windowmaker and blackbox, the line looks like this:
SessionTypes=kde;gnome;windowmaker;blackbox;anotherlevel;default;failsafe;
/etc/X11/xdm/Xsession. Here is what the appropriate section of
Xsession looks like before adding the new entries:
# now, we see if xdm/gdm/kdm has asked for a specific environment
#
case $# in
1)
case $1 in
failsafe)
exec xterm -geometry 80x24-0-0
;;
gnome)
exec gnome-session
;;
kde)
exec startkde
;;
anotherlevel)
# we assume that switchdesk is installed.
exec /usr/share/apps/switchdesk/Xclients.anotherlevel
;;
esac
esac
Here is what this section of the Xsession file looks like after adding the new entries (NOTE that the selection labels must be exactly the same in Xsession and prefdm, i.e., spelling and case must be identical):
# now, we see if xdm/gdm/kdm has asked for a specific environment
#
case $# in
1)
case $1 in
failsafe)
exec xterm -geometry 80x24-0-0
;;
gnome)
exec gnome-session
;;
kde)
exec startkde
;;
windowmaker)
exec wmaker
;;
blackbox)
exec blackbox
;;
anotherlevel)
# we assume that switchdesk is installed.
exec /usr/share/apps/switchdesk/Xclients.anotherlevel
;;
esac
esac
/usr/bin/
/usr/local/bin/
/usr/X11R6/bin/
/usr/bin/X11/
These examples should be enough for you to add your favorite window manager(s) to the KDE graphical login, or to give you a starting point to find out how it's done in your particular installation.
In RedHat 6.1, the default KDE login window shows a dialog box with a space to
type in the user name, one in which to type the user password, and a drop down
list to select the window manager/desktop environment of choice. By making the
following changes to /usr/share/config/kdmrc, user icons will appear in
the top of the login box.
Here is what the default lines that control user icon view in kdmrc look like (other
lines between these two are not shown, and are represented by "..."):
#Users=root;johndoe
...
UserView=false
Here are the same lines after editing; delete the comment character ("#") in front of "Users=..." and change "johndoe" to your username (if there are more user accounts on your system, you may add their usernames here, separated by semi-colons as shown). Change "UserView=false" to "UserView=true" as shown here:
Users=root;johnpipe
...
UserView=true
Now, when you login, you may click on an icon with the mouse to enter the user name; you must still type in your password.
You can add your own icons in place of the default icons; place you own icons in /usr/share/apps/kdm/pics/users/. They should be of size 64 x 64, according to the kdm handbook; in KDE 1.x, the default icons are 62 x 63, and my new user icon is 60 x 60, so if icons are reasonably close to the specified 64 x 64 size, they will work OK. The handbook says "kdm is able to handle icons of different sizes, but the result looks messy.", so there is evidently some leeway here. Your icons should be named 'username.xpm', for example my username is "johnpipe" and my new icon is named 'johnpipe.xpm'
NOTE: at some time since kde 1.x, the icon format has been changed from '.xpm' (XPixMap) to '.png' (portable network graphic).
The default for the shutdown button on the login box allows anyone to use it to shutdown the system.
The section in /usr/share/config/kdmrc controlling who may use this button looks like this:
#ShutdownButton=RootOnly
ShutdownButton=ConsoleOnly
To enable only the root user to shutdown the system, change the lines as shown below:
ShutdownButton=RootOnly
#ShutdownButton=ConsoleOnly
Clicking the shutdown button will now prompt for the root password before shutting down the system.
For more HOWTO's, see The Linux Documentation Project
Recommended reading:
Depending on your Linux distribution and version, you may already have the above HOWTO's installed on your system. If not installed, you may have them on your installation CD.