Linux Create a Custom Gnome Login Desktop Screen

Q. I'd like to keep same login screen for my school Linux desktop system lab. How do I create a custom gnome login screen or menu under CentOS or Ubuntu Linux desktop systems?

A. You can easily customize all properties of a login screen. You can manually edit the files or use GUI tool.

Editing configuration files

Different Linux distribution stores GDM config files under diffrent directories:

1. Debian / Ubuntu Linux: /etc/gdm directory
2. RHEL / CentOS / Red Hat / Fedora Linux : /etc/X11/gdm directory
3. OpenSuse / SUSE Linux : /etc/opt/gnome/gdm directory

Use ls command to view files:
$ ls -l /etc/gdm
Sample output:

-rw-r--r-- 1 root root 34141 2007-10-24 00:10 factory-gdm.conf
-rw-r--r-- 1 root root   132 2007-08-11 02:26 failsafeBlacklist
-rwxr-xr-x 1 root root  7343 2007-09-07 05:57 failsafeDexconf
-rwxr-xr-x 1 root root  1646 2007-10-07 22:26 failsafeXinit
-rwxr-xr-x 1 root root  6207 2007-10-07 22:25 failsafeXServer
-rw-r--r-- 1 root root 34141 2007-10-15 16:11 gdm.conf
-rw-r--r-- 1 root root  2175 2008-01-16 13:08 gdm.conf-custom
-rw-r--r-- 1 root root  1564 2007-04-11 02:12 gdmprefetchlist
drwxr-xr-x 2 root root  4096 2007-11-19 12:15 Init
-rw-r--r-- 1 root root 10842 2007-10-15 16:09 locale.conf
drwxr-xr-x 2 root root  4096 2007-11-19 12:15 modules
drwxr-xr-x 2 root root  4096 2007-11-19 12:15 PostLogin
drwxr-xr-x 2 root root  4096 2007-11-19 12:15 PostSession
drwxr-xr-x 2 root root  4096 2007-11-19 12:15 PreSession
-rwxr-xr-x 1 root root  4182 2007-10-15 16:11 XKeepsCrashing
-rwxr-xr-x 1 root root  6226 2007-10-15 16:12 Xsession

Usually, you need to only update gdm.conf file. However, this file should not be updated by hand. Since GDM 2.13.0.4, configuration choices in the GDM System Configuration file (gdm.conf) will override the default values specified in this file.

Gui tool

Type the following command to open GUI configuration tool:
# gdmsetup
or
$ sudo gdmsetup
Now you should able to customize login screen:

Fig. 01: gdmsetup in action

Note that not all configuration options are listed here. You may want to edit gdm.conf-custom if you cannot find what you are looking for.