When you start X, Debian runs some shell scripts that start your window manager
and other X clients. By default, a window manager, an xconsole, and
an xterm are started for you.
To customize your X startup, the file /etc/X11/config must contain
the line allow-user-xsession. If it does not, log in as root and add
the line now. Then log back in as yourself and continue the tutorial.
You can see how Debian's X startup works in the file /etc/X11/
Note that you can change the behavior of /etc/X11/Xsession by modifying
the file /etc/X11/config, which specifies a few system-wide preferences.
To run the clients of your choice when X starts, you create an executable shell
script called .xsession in your home directory.
$ touch ~/.xsession
This creates the file.
$ chmod u+x ~/.xsession
This makes the file executable.
Once .xsession is created, you need to edit it to do something useful
with your favorite text editor. You can do anything you want to in this script.
However, when the script's process terminates, X also terminates.
In practical terms, this means that you often end the script with a call to
exec. Whatever program you exec will replace the script process
with itself, so commands found after the exec line will be ignored.
The program you exec will become the new owner of the script process, which
means that X will terminate when this new program's process terminates.
Say you end your .xsession with the line exec fvwm. This means
that the fvwm window manager will be run when X starts. When you quit
the fvwm window manager, your X session will end, and all other clients
will be shut down. You do not have to use a window manager here; you could exec
xterm, in which case typing exit in that particular xterm
would cause the entire X session to end.
If you want to run other clients before you use exec, you will need
to run them in the background. Otherwise .xsession will pause until
each client exits and then continue to the next line. See the previous section
on running jobs in the background (basically you want to put an ampersand at
the end, as in xterm &).
You can take advantage of this behavior, though. If you want to run commands
at the end of your X session, you can have your .xsession run a window
manager or the like and wait for it to finish. That is, leave off the exec
and the &; just enter fvwm by itself. Then put the commands
of your choice after fvwm.
It would probably help to look at a few sample .xsession files. In
all the examples, replace fvwm with the window manager of your choice.
The simplest .xsession just runs a window manager:
This will run fvwm, and the X session will end when fvwm exits.
If you do it without the exec, everything will appear to behave the
same way, but behind the scenes .xsession will hang around waiting
for fvwm, and .xsession will exit after fvwm does.
Using exec is slightly better because fvwm replaces .xsession
instead of leaving it waiting. You can use the ps or top command
to verify this.
A more useful .xsession runs a few clients before starting the window
manager. For example, you might want some xterms and an xclock
whenever you start X. No problem; just enter xterm & xterm & xclock
& exec fvwm. Two xterms and an xclock start up in the background,
and then the window manager is launched. When you quit the window manager, you'll
also quit X.
You might try it without the backgrounding just to see what happens. Enter this
command: xterm xclock exec fvwm. xterm will start, and wait
for you to exit it. Then xclock will start; you'll have to exit xclock
before fvwm will start. The commands are run in sequence, since the
script waits for each one to exit.
You can use sequential execution to your advantage. Perhaps you want to keep
track of when you stop working every day:
date >> ~/logout-time
This will fork off an xterm and an xclock and then run fvwm
and wait for it to finish. When you exit fvwm, it will move on to the
last line, which appends the current date and time to the file ~/logout-time.
Finally, you can have a program other than the window manager determine when
This script will run xclock and fvwm in the background and
then replace itself with xterm. When you exit the xterm, your
X session will end.
The best way to learn how to use .xsession is to try some of these
things out. Again, be sure you use chmod to make it executable; failure
to do so is a common error.