Re: XDM setup, how to change default color depth

[Noel Yap <ivy1@cornell.edu>]

Chris R. Martin wrote:
> 
> How can I convince xdm that I want to run at a 32-bit color depth by
> default rather than 8 bpp?  Do I need to 'hack up' my XF86Config file so
> that 32 bpp is the only one availible, or can I somehow pass a parameter to
> the X server when it is started up?

The short answer:  Look in /etc/X11/xdm/Xserver

The long answer:

$ man xdm

NAME
       xdm  -  X  Display  Manager  with  support for XDMCP, host
       chooser
[...]
OVERVIEW
       xdm  is  highly configurable, and most of its behavior can
       be controlled by resource files and  shell  scripts.   The
       names  of  these  files themselves are resources read from
       the file xdm-config or  the  file  named  by  the  -config
       option.
[...]
RESOURCES
       At  many  stages  the  actions  of  xdm  can be controlled
       through the use of its configuration file, which is in the
       X  resource format.  Some resources modify the behavior of
[...]
       DisplayManager.servers
              This  resource either specifies a file name full of
              server entries, one per line (if the  value  starts
              with  a  slash), or a single server entry.  See the
              section Local Server Specification for the details.
[...]
CONFIGURATION FILE
       First, the xdm configuration file should be set up.   Make
       a  directory  (usually  <XRoot>/lib/X11/xdm, where <XRoot>
       refers to the root of the X11 install tree) to contain all
       of  the  relevant  files.  In the examples that follow, we
       use /usr/X11R6 as the value of <XRoot>.
[...]
       Note  that  this  file mostly contains references to other
       files.  Note also that some of the resources are specified
[...]

Debian puts the X11 configuration files in /etc/X11/ so if you look in
/etc/X11/xdm/xdm-config

$ cat /etc/X11/xdm/xdm-config
! /etc/X11/xdm/xdm-config
!
! resources specific to xdm itself
DisplayManager.authDir:         /var/lib/xdm
DisplayManager.errorLogFile:    /var/log/xdm-errors
DisplayManager.pidFile:         /var/run/xdm-pid
DisplayManager.keyFile:         /etc/X11/xdm/xdm-keys
DisplayManager.servers:         /etc/X11/xdm/Xservers
DisplayManager.accessFile:      /etc/X11/xdm/Xaccess
[...]

The DisplayManager.servers line xdm to look in /etc/X11/xdm/Xservers to
start the X server.

$ cat /etc/X11/xdm/Xservers
# /etc/X11/xdm/Xservers
# [Comments deleted]
:0 local /usr/X11R6/bin/X

So all you have to do is append the option `-bpp 16'.  Voila!

Noel