shutdown

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NAME

       shutdown - bring the system down


SYNOPSIS

       /sbin/shutdown [-t sec] [-rkhncf] time [warning-message]


DESCRIPTION

       Shutdown  brings  the  system  down  in a secure way.  All
       logged in users are notified  that  the  system  is  going
       down, and login(1) is blocked.  It is possible to shut the
       system down immideately, or after a delay.  All  processes
       are  first  notified  that the system is going down by the
       signal SIGTERM.  This gives programs like vi(1)  the  time
       to  save  the file being editted, mail and news processing
       programs a chance to exit cleanly, etc. Shutdown does it's
       job  by  signalling  the init process, asking it to change
       the runlevel.  Runlevel 0 is used to halt the system, run-
       level  6  is  used  to reboot the system and runlevel 1 is
       used to put to system into a  state  where  administrative
       tasks can be performed; this is the default if neither the
       -h or -r flag is given to shutdown.  To see which  actions
       are taken on halt or reboot see the appropriate entries of
       these runlevels in the file /etc/inittab.


OPTIONS

       -t sec Tell init to wait sec seconds between sending  pro-
              cesses  the  warning  and  the  kill signal, before
              changing to another runlevel.

       -k     Don't really shutdown; only send the  warning  mes-
              sages to everybody.

       -r     Reboot after shutdown.

       -h     Halt after shutdown.

       -n     [DEPRECIATED]  Don't  call  init to do the shutdown
              but do it ourself.  The use of this option is  dis-
              couraged, and its results are not always what you'd
              expect.

       -f     Do a `fast' reboot.

       -c     Cancel  an  already  running  shutdown.  With  this
              option it is ofcourse not possible to give the time
              argument, but you can enter a  explanitory  message
              on the command line that will be sent to all users.

       time   When to shutdown.

       warning-message
              Message to send to all users.

       The time argument can have different formats.   First,  it
       can  be  an absolute time in the format hh:mm, in which hh
       is the hour (1 or 2 digits) and mm is the  minute  of  the
       hour (in two digits).  Second, it can be in the format +m,
       in which m is the number of minutes to wait.  The word now
       is an alias for +0.

       The  -f  flag  means  `reboot fast'.  This only creates an
       advisory file /fastboot which can be tested by the  system
       when it comes up again.  The boot rc file can test if this
       file is present, and decide not to run fsck(1)  since  the
       system  has been shut down in the proper way.  After that,
       the boot process should remove /fastboot.

       The -n flag causes shutdown not to call init, but to  kill
       all  running  processes  itself.  After  all processes are
       killed,   shutdown   will   try   to   run   the    script
       /etc/rc.d/rc.halt  fast  (or rc.reboot). It also tests for
       the presence of the equivalent files  rc.0  and  rc.6.  If
       this script returns or can't be executed (because it's not
       present for example) shutdown  will  turn  off  quota  and
       accounting, turn off swapping and unmount all filesystems.


Access Control

       Shutdown can be called from init(8) when  the  magic  keys
       CTRL-ALT-DEL are pressed, by creating an appropriate entry
       in /etc/inittab. This means that everyone who has physical
       access  to  the console keyboard can shut the system down.
       To prevent this, shutdown can check to see  if  an  autho-
       rized user is logged in on one of the virtual consoles. If
       shutdown is called from init, it checks to see if the file
       /etc/shutdown.allow  is  present.   It  then  compares the
       login names in that file with the list of people that  are
       logged  in on a virtual console (from /var/run/utmp). Only
       if one of those authorized users or root is logged in,  it
       will proceed. Otherwise it will write the message

       shutdown: no authorized users logged in

       to the (physical) system console. The format of /etc/shut-
       down.allow is one user name per line. Empty lines and com-
       ment  lines (prefixed by a #) are allowed. Currently there
       is a limit of 32 users in this file.


FILES

       /fastboot
       /etc/inittab
       /etc/rc.d/rc.halt
       /etc/rc.d/rc.reboot
       /etc/shutdown.allow


BUGS

       Not really a bug, but most users forget to give  the  time
       argument  and  are then puzzled by the error message shut-
       down produces. The  time  argument  is  mandatory;  in  90
       percent of all cases this argument will be the word now.


AUTHOR

       Miquel van Smoorenburg, miquels@drinkel.ow.org


SEE ALSO

       fsck(8), init(1), halt(8), reboot(8)
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