As with all XFree86 configuration files, this is a plain text file, and is usually a simple, one line statement to start the X server. It can include any valid command line options supported by your X installation. If you always start X with your own options, this should be easier than typing the options each time. One possible ~/.xserverrc:

 exec X :0 -dpi 100 -nolisten tcp

 

This will start X on display :0, the first “display”, at a dots-per-inch resolution of 100, and disables TCP connections. See the Xserver man page for other valid options. This is just an example.

xinitrc is used to set up a suitable X environment, and to launch other programs, a.k.a “clients” that we may want available as soon as X is started. You likely have a system wide xinitrc to start a predefined set off programs. To customize this, create your own in your home directory. Name it .xinitrc, make sure it is an executable script, and chmod +x. An example (slightly modified from the original on my system):

#!/bin/sh
# $XConsortium: xinitrc.cpp,v 1.4 91/08/22 11:41:34 rws Exp $

userresources=$HOME/.Xresources
usermodmap=$HOME/.Xmodmap

# merge in defaults and keymaps
if [ -f $userresources ]; then
    xrdb -merge $userresources
fi

if [ -f $usermodmap ]; then
    xmodmap $usermodmap
fi

if [ -z "$BROWSER" ] ; then
	# we need to find a browser on this system
	BROWSER=`which netscape`
	if [ -z "$BROWSER" ] || [ ! -e "$BROWSER" ] ; then
	# not found yet
		BROWSER=
	fi
fi
if [ -z "$BROWSER" ] ; then
	# we need to find a browser on this system
	BROWSER=`which lynx`
	if [ -z "$BROWSER" ] || [ ! -e "$BROWSER" ] ; then
	# not found yet
		BROWSER=
	else
		BROWSER="xterm -font 9x15 -e lynx"
	fi
fi

export BROWSER

# start some nice programs
if [ -f $HOME/.Xclients ]; then
    exec $HOME/.Xclients
else
    xclock -geometry 50x50-1+1 &
    xterm -geometry 80x50+494+51 &
    if [ -f /usr/X11R6/bin/fvwm ]; then
        exec fvwm
    else
        exec twm
    fi
fi

#eof

 

Briefly, what this script does, is set up our working environment, with xmodmap (keyboard) and xrdb (application resource settings). More on these below. Then the shell variable $BROWSER is set for a GUI environment (Netscape in this example) so that any applications that might expect this, have a reasonable choice available. Then the presence of the file Xclients is checked, both as a system wide file and in the user's home directory. In this particular example, this is where any client applications are to be started, including a Window Manager (see below). These could just have as easily been started here if we had wanted to. If an Xclients file can't be found, then a Window Manager is started for us. Either fvwm, if available, or XFree86's minimalist twm if not. If for some reason, neither of these can be started, the script would exit, and X would fail to start.

Everything up to this point has followed pretty much a standard and predictable sequence of events. To summarize, we have invoked startx, which in turn invoked xinit, which has parsed xinitrc for initial settings. Most Linuxes should follow this same sequence, though the various values and settings may differ.

We now are at the last link in the chain where the user normally would specify his or her preferences, including the Window Manager and/or desktop environment to be used. The system will provide sane, though possibly uninteresting, defaults if the user has not done so. Presumably, this is why you are here ;-)

The Window Manager, or desktop environment, is typically the last application started. If you want other programs (like xterm) started, they should be started before the Window Manager and “backgrounded” with an “&”. This can all be done in the user's ~/.xinitrc. Or as in the above example, the actual applications are started from yet another script. Let's look at one short, hypothetical such script, .Xclients:

 
#!/bin/bash
# ~/.Xclients, start my programs.

xset s off s noblank
xset m 30/10 4
xset r rate 200 40

xscreensaver & 
rxvt -geometry 80x50-50+150 &

echo Starting Window Manager...

if [ -x /usr/X11R6/bin/wmaker ]; then
  echo `date`: Trying /usr/X11R6/bin/wmaker... |tee -a ~/.wm-errors 2>&1
  exec /usr/X11R6/bin/wmaker >> ~/.wm-errors 2>&1
fi 

echo `date`: Failed, trying fvwm... |tee -a ~/.wm-errors 2>&1

# let's try regular fvwm (AnotherLevel doesn't work with fvwm1).
if [ -n "$(type -path fvwm)" ]; then
  # if this works, we stop here
  exec fvwm >> ~/.wm-errors 2>&1
fi

echo `date`: Failed, trying twm... |tee -a ~/.wm-errors 2>&1

# wow, fvwm isn't here either ... 
# use twm as a last resort.
exec twm >> ~/.wm-errors 2>&1

# Dead in the water here, X will exit as well, sigh...
echo `date`: Unable to start a Window Manager ... |tee -a ~/.wm-errors 2>&1

# eof

 

This really isn't so different than what xinitrc was doing at all. We added a few wrinkles, including starting a screen saver, a different terminal emulator that this user prefers (rxvt), with even more setting up of the environment (monitor, mouse and keyboard) using xset this time, and a different Window Manager than was available with the system defaults. This is in the user's home directory, so it will not be overwritten during upgrades too.

Actually, X has already started at this point, and we are just putting the finishing touches on the configuration. Notice the Window Managers are not “backgrounded” with “&” here. This is important! Something has to run in the foreground, or X will exit. We didn't start a desktop environment in this example, like KDE or GNOME, but if we did, this final application would have to be gnome-session or startkde instead. Since we are rolling our own here, if we wanted to change Window Managers, all we have to do is edit this file, and restart X. Vendor supplied configurations may be more complex than this, but the same principles apply.

As an afterword, do not think that any initial client applications must be started as we've done here. This is how it has been traditionally done, and some may prefer this approach. Most window managers have their own built-in ways to start initial programs, as do KDE and GNOME. See the respective documentation.

xdm can be configured with configuration files located in /etc/X11/xdm/, /usr/X11R6/lib/X11/xdm, or similar locations depending on your system. These are system wide files. The file xdm-config is the main configuration file, and mostly describes where to find secondary configuration files:

 ! $XConsortium: xdm-conf.cpp /main/3 1996/01/15 15:17:26 gildea $
 DisplayManager.errorLogFile:	/var/log/xdm-errors
 DisplayManager.servers:		/etc/X11/xdm/Xservers
 DisplayManager.accessFile:	/etc/X11/xdm/Xaccess
 ! All displays should use authorization, but we cannot be sure
 ! X terminals will be configured that way, so by default
 ! use authorization only for local displays :0, :1, etc.
 DisplayManager._0.authorize:	true
 DisplayManager._1.authorize:	true
 ! The following three resources set up display :0 as the console.
 DisplayManager._0.setup:	/etc/X11/xdm/Xsetup_0
 DisplayManager._0.startup:	/etc/X11/xdm/GiveConsole
 DisplayManager._0.reset:	/etc/X11/xdm/TakeConsole
 !
 DisplayManager*resources:	/etc/X11/xdm/Xresources
 DisplayManager*session:		/etc/X11/xdm/Xsession
 !
 ! SECURITY: do not listen for XDMCP or Chooser requests
 ! Comment out this line if you want to manage X terminals with xdm
 DisplayManager.requestPort:	0

 

The “!” denotes comments. The command that starts the X server is in /etc/X11/xdm/Xservers in this particular example as defined by “DisplayManager.servers”, and is the equivalent to xserverrc that was used for startx X server start up commands, but the syntax is slightly different here. The contents of /etc/X11/xdm/Xservers on my system are simply:

 :0 local /usr/X11R6/bin/X 

 

This starts X on the first local display (designated by 0). Any special command line arguments that you want to add go here at the end.

Below is a sample /etc/X11/xdm/Xsetup_0 which is used to configure the log-in screen only. Notice that we're using a shell script here, and it's calling xv (a graphics display program) to set the background to a nice image (instead of the boring black and white background pattern), and if that fails, xsetroot is then invoked to at least try to set the background to a nicer blue color. This does not configure the login widget itself -- just other things that might be wanted on the screen during login.

 
 #!/bin/sh
 xconsole -geometry 480x100-0-0 -daemon -notify -verbose -fn \
   '-schumacher-clean-medium-r-*-*-10-*-*-*-*-*-*-*' -exitOnFail  &
 
 /usr/X11R6/bin/xv -quit -root /usr/share/pixmaps/Backgrounds/InDreams.jpg \
   || xsetroot -solid darkblue
 
 

/etc/X11/xdm/Xresources controls the X “resources” used during log in. In this context, “resources” are user preferences for such items as fonts and colors (described in more detail below). Below is a snippet that sets up fonts for the log-in widget:

 #if WIDTH > 800
 xlogin*greetFont: -adobe-helvetica-bold-o-normal--24-240-75-75-p-138-iso8859-1
 xlogin*font: -adobe-helvetica-medium-r-normal--18-180-75-75-p-103-iso8859-1
 xlogin*promptFont: -adobe-helvetica-bold-r-normal--18-180-75-75-p-103-iso8859-1
 xlogin*failFont: -adobe-helvetica-bold-r-normal--18-180-75-75-p-103-iso8859-1
 #else
 xlogin*greetFont: -adobe-helvetica-bold-o-normal--17-120-100-100-p-92-iso8859-1
 xlogin*font: -adobe-helvetica-medium-r-normal--12-120-75-75-p-69-iso8859-1
 xlogin*promptFont: -adobe-helvetica-bold-r-normal--12-120-75-75-p-69-iso8859-1
 xlogin*failFont: -adobe-helvetica-bold-o-normal--14-140-75-75-p-82-iso8859-1
 #endif

 

As you can see this is using helvetica as the preferred font, with different point sizes and dots per inch depending on the screen size. This is customizable to suit individual needs. (See below for more on understanding X font naming conventions.) Various other aspects can similarly be configured.

/etc/X11/xdm/Xsession is the rough equivalent to xinitrc for startx. It will similarly set up a default environment for keyboard, etc. And can also start either KDE or GNOME, and other X client programs. This is the system wide configuration file. It should also check the user's home directory for ~/.xsession, and possibly ~/.Xclients, which would contain the user's preferred environment and start up programs, just as ~/.xinitrc did with startx. Again, the files in a user's home directory may be created or modified by the user any time and must be executable shell scripts.

We shall not include an ~/.xsession example here, since it would be very similar to the ~/.xinitrc and ~/.Xclients examples above.

We've looked only briefly at the main xdm configuration files. Be sure to read the man page, and look at what is installed locally, for more information. Let's look now at gdm and kdm. We'll just highlight significant differences, since they essentially provide the same functionality.

gdm is the default display manager for GNOME. gdm was written from scratch, but functions similarly to xdm. The main configuration file is gdm.conf, typically located as /etc/X11/gdm/gdm.conf. This is quite different looking than xdm-config. Comments are denoted with a “#”, and the file has sections, with section headers enclosed in square brackets. The command to start X is in the “[servers]” section:

 [servers]
 0=/usr/bin/X11/X
 #1=/usr/bin/X11/X

 

Notice this has potentially two displays set up, but the second one is commented out. Add any additional X startup options here, e.g. “-dpi 100”. The log-in screen and log-in widget are configured in the “[greeter]” section.

Start up clients and programs are determined by the “SessionDir” statement in the “[daemon]” section. On my installation, this points to /etc/X11/gdm/Sessions/, which contains several short scripts. If I look at my Default script, it actually executes /etc/X11/xdm/Xsession, which in turn would execute ~/.xsession, if present. So at this final stage, gdm acts very much like xdm.

GNOME includes the gdmconfig utility to control many aspects of gdm behavior.

kdm is the display manager from KDE. The main configuration file for kdm is kdmrc and is typically installed as /etc/kde/kdm/kdmrc. As is the case with gdm.conf, kdmrc uses “#” for comments, and has sections with section headers in similar square brackets. kdm configuration can also be edited with the kcontrol utility.

The visible desktop is configured in the “[Desktop*]” section(s), and by the “Setup” directive which should point to a file like /usr/share/config/kdm/Xsetup or /etc/X11/xdm/Xsetup_0. This will accomplish the same thing as xdm's Xsetup_0 does: namely running any programs the user might want such as xconsole.

The command to launch the X server is the “Xservers” directive in the “[General]”. Again, this should point to a file such as /etc/X11/xdm/Xservers, and uses the same syntax as xdm:

 :0 local /usr/X11R6/bin/X 

 

Any command line options for the X server, go here.

The login widget itself is configured in the “[X-*-Greeter]” section(s). Compiled in defaults are used if the user does not specify any.

KDE includes the kdmdesktop utility to control some aspects of kdm behavior, mostly just the login background.