[ale] xinit, autoexec, xorg, gdm, kdm, etc.etc.,

[Byron Jeff]

Finally a post that got me off my butt and resubscribe under my new E-mail
address.

It's good to be back.

On Wed, Dec 22, 2010 at 04:15:50PM -0500, Narahari 'n' Savitha wrote:
> Friends:
> 
> I am a linux user on the command line with low key know-how.
> 
> How does the X stuff fit it, I am not sure.

X is the premier Unix windowing system and more. It has built in mechanisms
for projecting interfaces from applications (which are considered to be
clients) to displays (which are called X servers). The vast majority of the
time they run on the same machine. But you can run an app pretty much
anywhere and see its output on your local machine.

> 
> What role does XINITRC play ?

xinit is an application that does two primary tasks:

1) It starts a local X server
2) It sets up the initial set of clients to run on that server. The vast
majority of the time this is the window manager of the users choice.

> What role does, xorg.conf play ?

When present, it configures the X server. It defines what video cards,
monitors, input devices, and screen resolutions are used. In addition it
can also specify any extensions and layouts (multiple screens for example)
that the server should configure itself for. In short, it's the primary
configuration file for the X server.

In its absence, an X server will attempt to autodetect all of these items.

> 
> When I del xorg.conf, connect my TV and run the dpkg blah blah, xorg.conf get created but not sure if it refers to the tv.

X servers output their log files in /var/log for the most part. The first
server will have a log file named Xorg.0.log. In there it will tell you
what devices it is using. So for example my log has the following displays
connected:

[    84.155] (--) NVIDIA(0): Connected display device(s) on GeForce 7600 GS at PCI:1:0:0
[    84.155] (--) NVIDIA(0):     CRT-1
[    84.155] (--) NVIDIA(0):     Acer P235H (DFP-0)

> 
> What files do gdm and/or kdm use for configuration ?

I know that the kdm files are located in /etc/kde4/kdm/kdmrc
I'm unsure about gdm off the top of my head.

> 
> Please provide some links I can read.

I would caution about getting too in depth about the whole process
initially. The X/xinit/(xdm,kdm,gdm) system has been well tuned to
generally give useful results with the defaults.

A good idea is simply to run the X server from the command line:

prompt$ X

and take a read of the log file that it produces. Often it will give you
sufficient clues to figure out how to get things going without having to
try to figure out everything.

I just went through the process of figuring out everything in the process
of putting together a multi-user workstation. It fires up a dual headed X
server with no input devices, then kdm starts two instances of the Xephyr
nested server, one for each screen and each with their own keyboard and
mouse. Two different kdm login screens are put on each nested server. All
done on a Kubuntu 10.10 box.

Hope this helps,

BAJ

> 
> -Narahari

-- 
Byron A. Jeff
Department Chair: IT/CS/CNET
College of Information and Mathematical Sciences
Clayton State University
http://cims.clayton.edu/bjeff