Provided by: xdm_1.1.11-3ubuntu2_amd64 bug


       xdm.options - configuration options for the X display manager


       /etc/X11/xdm/xdm.options  contains  a  set of flags that determine some of the behavior of
       the X display manager xdm(1x).  Most of xdm's behavior is customized through other  files;
       consult the xdm manual page if this manual page does not describe the behavior you want to

       /etc/X11/xdm/xdm.options may contain comments, which begin with a hash mark (‘#’) and  end
       at  the  next newline, just like comments in shell scripts.  The rest of the file consists
       of options which are expressed as words separated by hyphens, with  only  one  option  per
       line.   Options  are  enabled  by  simply  placing  them in the file; they are disabled by
       prefixing the option name with ‘no-’.

       Available options are:

              Normally, if the nologin(5) file exists,  its  contents  will  be  displayed  using
              xmessage(1x)  (if  xmessage is available), and the user will be returned to the xdm
              login screen after xmessage is dismissed instead of starting  the  X  session.   If
              this option is enabled, xdm starts a session as usual (after xmessage is dismissed,
              if xmessage is available and the nologin file exists).  This behavior  is  disabled
              by default: nologin is heeded, not ignored.

              Enable  this  option with caution on ‘production’ machines; it causes the daemon to
              be stopped and restarted on upgrade, even if the process has children (which  means
              it  is  managing  X  sessions).  Typically when a package that contains a daemon is
              being installed or upgraded, its maintainer scripts stop a running  daemon  process
              before installing the new binary, and restart it after the new binary is installed.
              Stopping xdm causes immediate termination of  any  sessions  it  manages;  in  some
              situations  this could be an unwelcome surprise (for instance, for remote xdm users
              who had no idea the administrator was performing system maintenance).  On the other
              hand,  for  machines  that stay up for long periods of time, leaving the old daemon
              running can be a bad idea if the new  version  has,  for  instance,  a  fix  for  a
              security  vulnerability  (overwriting  xdm's  executable  on the file system has no
              effect on the copy of xdm in memory).  The xdm package's pre-removal script  checks
              to  see  if  the  xdm  process  has  any  children; if it does, it is possible that
              someone's session would be killed by stopping xdm, so a warning is  issued  and  an
              opportunity  to  abort the upgrade of xdm is provided.  Furthermore, restarting xdm
              on upgrade can be surprising, because a locally-managed X  server  can  change  the
              active  VT  even  while other packages are continuing to upgrade.  If, by intent or
              accident, the X server does not honor the key sequence to  switch  VTs  back  to  a
              virtual  console,  this  can be undesirable.  This behavior is disabled by default:
              xdm will be not be stopped or  started  during  an  upgrade  of  its  package;  the
              administrator  will  have  to  do  so  by  hand (with invoke-rc.d xdm restart or by
              rebooting the system) before the newly installed xdm binary is used.

              Enable this option with caution; it causes the xdm daemon to be started immediately
              after  the  package is installed.  See the above entry regarding restart-on-upgrade
              for other caveats regarding the consequences of  starting  the  xdm  daemon  during
              package  management.  This behavior is disabled by default: xdm will not be started
              when it is installed.  Changing this setting can  affect  future  installs  if  the
              package   is   removed,  but  not  purged  (which  removes  ‘conffiles’,  including

              This option causes the /etc/X11/xdm/Xreset script to call the  sessreg(1x)  program
              to  register  X sessions managed by xdm in the utmp(5) and wtmp(5) files.  If it is
              disabled, the utmp and wtmp files will  have  no  record  of  xdm  sessions.   This
              behavior is enabled by default; sessreg will be used.

       Users  of  older  versions of the Debian system should note that the ‘run-xconsole’ option
       has been removed.  The shell script named /etc/X11/xdm/Xreset can be edited to disable  or
       modify  the  running  of  xconsole  on  the  xdm  greeter  screen;  see  xdm(1x)  for more


       Stephen Early, Mark Eichin, and  Branden  Robinson  customized  xdm's  startup  and  reset
       scripts  and  package  maintainer  scripts to implement the functionality described above.
       This manual page was written by Branden Robinson.


       sessreg(1x), xmessage(1x), xdm(1x), nologin(5), utmp(5), wtmp(5)