Gnome Display Manager usage with the Linux Terminal Server Project

May 7 2002 updated for gdm-2.2.5.5

This Howto addresses the use of the Gnome Display Manager (gdm) with the LTSP project to provide a more modern graphical login to the LTSP. GDM has many advantages over XDM and you should really read the fine reference by Martin K. Peterson. I will assume that the reader knows how to set up a server for disk-less workstation booting. Also assumed is the current version of LTSP and a working Redhat 6.2 thru 7.1 server.


About GDM

GDM is the Gnome Display Manager. It has the same basic functionality of XDM or KDM. GDM uses the same GiveConsole TakeConsole and Xsetup_0 as xdm, these can be symlink from /gdm/PreSession/Default, /gdm/PostSession/Default and /gdm/Init/Default or can be located in those directories. If you want to use the face browser you'll need to put a picture in a users /home/ username /.gnome directory named photo (no file extension) in jpeg, xpm, gif type format, also size the picture small enough. There is a gui configuration tool for gdm named gdmconfig, although it seems to be missing in some gnome releases.

An interesing use for GDM

One really big difference between GDM and XDM is that xdm grabs the keyboard focus and gdm does not, at least as of version 2.2.5.5. Using gdm allows you to set up a kiosk style terminal very easily, just add a line near the top of Xsetup_0 or /gdm/Init/default, whichever your gdm uses, that starts a program i.e xterm -e netscape. That will start an xterm and run netscape before gdm starts and keep the gdm login screen from starting until the program started by the xterm exits. Please note that xdmcp is a display manager not a window manager and any programs that are started will not have the wm widgets (decorations) attached.

GDM Display Manager setup

The first thing to do is to setup the Gnome Display Manager. This turned out to be very easy to do since I already had learned how to customize XDM. Please read and understand how to setup and customize XDM if you don't already know how to do this ( this is a must because GDM uses some of XDM's config files - Xsetup_0). Also you must have a working XDM for your workstations, again because GDM uses some of the config files from XDM. You must edit the GDM config file /etc/X11/gdm/gdm.conf. The gdm config file is very orderly and easy to understand, most options are 0 for off or 1 for on in older gdm versions and false for off or true for on in newer gdm versions. Stay with the format your gdm.conf file uses . The file is mostly configured correctly but needs a few options turned on:

The above is the minimum to get gdm to work for diskless workstations.


Putting it all together


If you have correctly modified the above mentioned files all that is left to do is start gdm and boot a workstation. If you had xdm working gdm will work. GOOD LUCK and let me know of any new twists that you find so they may be shared in future updates to this howto.

  1. First kill XDM. After stopping xdm you need to start gdm: #bash:gdm. Something to note here is that you don't need the server to be in runlevel5 to use the graphical logins, you just need to turn them on ( after proper configuration ). XDM does not always want to be completely killed on my system - reboot to insure the death of xdm. Also start gdm before any other window manager.
  2. Boot a workstation and gdm should come-up as the login display manager.


Some Points of Interest: aka troubleshooting



Links of interest


Gnome Display Manager. Everything you need for gdm can be found here http://www.gnome.org


Credits



* Martin K. Peterson for all his effort on gdm. http://www.gnome.org

* Jim McQuillan for his excellent LTSP project www.ltsp.org

* Jim Massey - author of this howto mailto:massey@stlouis-shopper.com