Provided by: xinit_1.0.1-0ubuntu3_i386 bug

NAME

       Xsession - initialize X session

SYNOPSIS

       Xsession [ session-type ]

DESCRIPTION

       /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 unfamilar 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
       programs handle this.

       By default on a Debian system, Xsession is used by both common  methods
       of  starting  the  X Window System, xdm and startx.  To change this for
       xdm,   edit    the    ‘DisplayManager*session’    resource    in    the
       /etc/X11/xdm/xdm-config  file;  for startx, 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
       itself.  See “CUSTOMIZING THE STARTUP PROCEDURE” below.

   SESSION TYPES
       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, and there is no way to pass Xsession an argument from  startx
       or xinit.  By default, three different arguments are supported:

       failsafe
              invokes       a      session      consisting      solely      of
              /usr/bin/x-terminal-emulator (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 Xsession.options.

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

       program
              starts program if it can be found in the $PATH.  This is usually
              a  session  manager  or  a  very  featureful window manager.  If
              program 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
              administrator  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.)

   DEFAULT STARTUP PROCEDURE
       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 user’s session, not just error messages.  If  it  is
       impossible  to  write  to  an  error  file,  the script (and thus the X
       session) 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
       easier  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
       confirmed to be present, Xsession uses an  internal  implementation  of
       run-parts(1) to identify files in that directory that should be sourced
       (executed) in the shell’s environment.  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 experimental 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.)

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

       /etc/X11/Xsession.d/20xfree86-common_process-args
              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.

       /etc/X11/Xsession.d/30xfree86-common_xresources
              X  resources  are merged.  The internal 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
              user’s $HOME/.Xresources file is merged in the same way.

       /etc/X11/Xsession.d/50xfree86-common_determine-startup
              Determine  startup  program.   The  X  client  to  launch as the
              controlling 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.

       /etc/X11/Xsession.d/90xfree86-common_ssh-agent
              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
              functionality may move to the ssh package in the future.

       /etc/X11/Xsession.d/99xfree86-common_start
              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 shell’s exec command is used to spare a slot  in
              the process table.

   CUSTOMIZING THE STARTUP PROCEDURE
       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;

       * an underscore;

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

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

       SYSMODMAP="/etc/X11/Xmodmap"
       USRMODMAP="$HOME/.Xmodmap"

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

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

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

   BUILT-IN SHELL FUNCTIONS
       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 user’s 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.

ENVIRONMENT

       The following environment variables affect the execution of Xsession:

       HOME   The user’s home directory; various files are searched for  here.

       TMPDIR 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.

       COLUMNS
              Width   of  terminal  device,  in  character  cells.   Used  for
              formatting diagnostic messages.

INPUT FILES

       /etc/X11/Xsession.d/
              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.

       /etc/X11/Xresources/
              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.

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

       $HOME/.Xresources
              contains   X   resources   specific   to   the  invoking  user’s
              environment.  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
              deprecated  for  over  ten  years  at  the time of this writing.
              .Xresources should be used instead.

       $HOME/.Xsession
              is a sequence of commands  invoking  X  clients  (or  a  session
              manager  such as xsm(1x)).  See the manual page for xinit and/or
              /usr/share/doc/xfree86-common/examples/xsession  for   tips   on
              writing an .Xsession file.

OUTPUT FILES

       $HOME/.xsession-errors
              Where standard output and standard error for Xsession script and
              all X client processes are directed by default.

       $TMPDIR
              Where   the   X   session    error    file    is    placed    if
              $HOME/.xsession-errors   cannot  be  opened.   The  filename  is
              provided by tempfile(1).

SEE ALSO

       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)

AUTHOR

       /etc/X11/Xsession  and its associated files in /etc/X11/Xsession.d were
       written by Stephen Early, Mark Eichin, and Branden Robinson.