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Xsession(5)							   Xsession(5)

       Xsession - initialize X session

       Xsession [ session-type ]

       /etc/X11/Xsession is a Bourne shell (sh(1)) script which is run when an
       X Window System session is begun by startx(1x)  or  a  display  manager
       such  as  xdm(1x).   (Some  display  managers only invoke Xsession when
       specifically directed to so by the user; see the documentation for your
       display	manager to find out more.)  Administrators unfamiliar with the
       Bourne shell will likely  find  the  Xsession.options(5)  configuration
       file easier to deal with than Xsession itself.

       Xsession  is  not  intended  to	be invoked directly by the user; to be
       effective it needs to run in a special environment  associated  with  X
       server  initialization.	startx, xdm, xinit(1x), and other similar pro
       grams handle this.

       By default on a Debian system, Xsession is used by both common  methods
       of starting the X Window System, xdm (or another X display manager) and
       startx.	To change this	for  xdm,  edit  the  DisplayManager*session
       resource  in  the /etc/X11/xdm/xdm-config file  for other display man
       agers, consult their documentation.  To stop startx from using Xsession
       by default, replace the contents of the /etc/X11/xinit/xinitrc file.

       The  Xsession  script is quite flexible, and extensive customization of
       the X startup  procedure  is  possible  without	modifying  the	script

       Xsession may optionally be passed a single argument indicating the type
       of X session to be started.  It is up to the display manager to set the
       argument.   To	pass  Xsession	an  argument  from  startx  or	xinit,
       /etc/X11/Xsession (or /etc/X11/xinit/xinitrc) must be called explicitly
       with  a	path,  as  in  startx /etc/X11/Xsession failsafe.  By default,
       three different arguments are supported:

	      invokes a session consisting solely of an x-terminal-emulator(1)
	      (no  window  manager  is	launched).  If the x-terminal-emulator
	      program cannot be found,	the  session  exits.   The  failsafe
	      argument	is  ignored  if  there	is no allow-failsafe line in

	      produces the same behavior as if no session  type  argument  had
	      been given at all.

	      starts program if it can be found in the $PATH.  This is usually
	      a session manager or a very featureful window manager.  If  pro
	      gram is not found, the Xsession script proceeds with its default
	      behavior.   This	argument   is	ignored   if   there   is   no
	      allow-user-xsession  line in Xsession.options.  (If the admin
	      istrator does not want users writing their own .xsession	files,
	      it  makes  little  sense	to permit them to specify the names of
	      arbitrary programs to run.)  Note that the  restriction  may  be
	      easy to bypass, e.g. by using a .gnomerc file instead.

       Initially,  Xsession  performs some housekeeping.  It declares a set of
       built-in  functions  (see  BUILT-IN  SHELL   FUNCTIONS	below)	 and
       variables,  then  attempts  to  create a log file for the X session, or
       append to an existing one.  Historically  this  is  called  an  error
       file,  but  it  catches	all  sorts of diagnostic output from various X
       clients run in the users session, not just error messages.  If  it  is
       impossible  to  write to an error file, the script (and thus the X ses
       sion) aborts.  For convenience, once the  error	file  is  successfully
       opened,	Xsession  reports  the	fact that the session has started, the
       invoking username, and the date to the error file.  This makes it  eas
       ier  to discern which X session produced a particular line of output in
       the file.

       Xsession next confirms that its script directory,  Xsession.d,  exists.
       If  it does not, the script aborts.  After the script directory is con
       firmed to be present, Xsession uses run-parts(1) to identify  files  in
       that  directory	that should be sourced (executed) in the shells envi
       ronment.  Only files named in  a  certain  way  are  sourced;  see  the
       run-parts  manual  page	for  a	description of valid characters in the
       filename.  (This restriction enables the administrator to move  experi
       mental  or problematic files out of the way of the script but keep them
       in an obvious place, for instance  by  renaming	them  with  .old  or
       .broken appended to the filename.)

       Five  shell  script  portions  are  supplied  by  default to handle the
       details of the session startup procedure.

	      Arguments are processed as described in SESSION  TYPES  above.
	      The  startup  program,  if  one  is identified at this point, is
	      merely stored for later reference, and not immediately executed.

	      X  resources  are merged.  run-parts is again used, this time to
	      identify files in the /etc/X11/Xresources directory that	should
	      be   processed   with   xrdb   -merge.	Next,  if  the	line
	      allow-user-resources  is	present  in  Xsession.options,	 the
	      users $HOME/.Xresources file is merged in the same way.

	      Source  global  environment  variables.  This script will source
	      anything in $HOME/.xsessionrc  if  the  file  is	present.  This
	      allows  the user to set global environment variables for their X
	      session, such as locale information.

	      Determine startup program.  The X client to launch as  the  con
	      trolling	process  (the  one  that,  upon  exiting, causes the X
	      server to exit as well) is determined next.   If	a  program  or
	      failsafe	argument  was  given and is allowed (see above), it is
	      used  as	the  controlling  process.   Otherwise,  if  the  line
	      allow-user-xsession   is	 present   in	Xsession.options,  a
	      user-specified session program or script is used.  In the latter
	      case,  two historically popular names for user X session scripts
	      are searched for: $HOME/.xsession and $HOME/.Xsession (note  the
	      difference  in  case).   The  first  one	found is used.	If the
	      script is not executable, it is marked to be executed  with  the
	      Bourne  shell  interpreter,  sh.	 Finally, if none of the above
	      succeeds,   the	following   programs   are    searched	  for:
	      /usr/bin/x-session-manager,    /usr/bin/x-window-manager,    and
	      /usr/bin/x-terminal-emulator.  The first one found is used.   If
	      none are found, Xsession aborts with an error.

	      Start  ssh-agent(1),  if needed.	If the line use-ssh-agent is
	      present in Xsession.options, and no SSH agent process appears to
	      be  running  already,  ssh-agent is marked to be used to execute
	      the startup program determined previously.  Note: this function
	      ality may move to the ssh package in the future.

	      Start  the X session.  The startup program is executed, inside a
	      Bourne shell if it is not executable, and inside an ssh-agent if
	      necessary.   The shells exec command is used to spare a slot in
	      the process table.

       Of course, any of the existing files can be edited in place.

       Because the order in which the various scripts  in  /etc/X11/Xsession.d
       are  executed  is important, files to be added to this directory should
       have a well-formed name.  The following format is recommended:

       * a two-digit number denoting sequence;

       * the name of  the  package  providing  the  script  (or  custom  for
       locally-created scripts);

       * an underscore;

       *  a  description of the scripts basic function, using only characters
       allowed by run-parts.

       Here is an example of how  one  might  write  a	script,  named	40cus
       tom_load-xmodmap, to invoke xmodmap(1x):


       if [ -x /usr/bin/X11/xmodmap ]; then
	   if [ -f "$SYSMODMAP" ]; then
	       xmodmap "$SYSMODMAP"

       if [ -x /usr/bin/X11/xmodmap ]; then
	   if [ -f "$USRMODMAP" ]; then
	       xmodmap "$USRMODMAP"

       Those  writing  scripts for Xsession to execute should avail themselves
       of its built-in shell functions, described below.

       message is used for communicating with the user.  It is a  wrapper  for
       the  echo(1)  command and relies upon echo for its argument processing.
       This function may be given an arbitrarily long message string, which is
       formatted  to  the users terminal width (breaking lines at whitespace)
       and sent to standard error.  If the DISPLAY environment variable is set
       and  the  xmessage(1x)  program	is available, xmessage is also used to
       display the message.

       message_nonl is used for communicating with the user  when  a  trailing
       newline	is  undesirable;  it omits a trailing newline from the message
       text.  It otherwise works as message.

       errormsg is used for indicating an error  condition  and  aborting  the
       script.	 It  works as message, above, except that after displaying the
       message, it will exit Xsession with status 1.

       The following environment variables affect the execution of Xsession:

       HOME   specifies the users home directory; various files are  searched
	      for here.

       TMPDIR names a default directory for temporary files; if the standard X
	      session error file cannot be opened, this variable  is  used  to
	      locate a place for one.

	      indicates the width of terminal device in character cells.  This
	      value is used for formatting diagnostic messages.

	      is a directory containing Bourne shell scripts to be executed by
	      Xsession.   Files  in this directory are matched using run-parts
	      and are sourced, not executed in a subshell.

	      is a directory containing files corresponding to Debian  package
	      names,  each  of	which contains system-wide X resource settings
	      for X clients from the corresponding package.  The settings  are
	      loaded  with  xrdb  -merge.  Files in this directory are matched
	      using run-parts.

	      contains configuration options for the /etc/X11/Xsession script.
	      See Xsession.options(5) for more information.

	      contains	X  resources  specific to the invoking users environ
	      ment.  The settings are loaded  with  xrdb  -merge.   Note  that
	      $HOME/.Xdefaults	is a relic from X Version 10 (and X11R1) days,
	      before app-defaults files were implemented.  It has been	depre
	      cated  for  over	ten  years at the time of this writing.  .Xre
	      sources should be used instead.

	      is a sequence of commands invoking X clients (or a session  man
	      ager  such  as xsm(1x)).	See the manual page for xinit for tips
	      on writing an .xsession file.

	      is where standard output and standard error for Xsession	script
	      and all X client processes are directed by default.

	      is  where  the  X  session  error file is placed if $HOME/.xses
	      sion-errors cannot be opened.  For security reasons,  the  exact
	      filename is randomly generated by tempfile(1).

       Stephen	Early,	Mark Eichin, and Branden Robinson developed Debians X
       session handling scripts.  Branden Robinson wrote this manual page.

       Xsession.options(5),  X(7x),  run-parts(1),  ssh-agent(1),  startx(1x),
       tempfile(1), xdm(1x), xmessage(1x), xmodmap(1x), xrdb(1x), sh(1)

Debian Project			  2004-11-04			   Xsession(5)

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