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SHUTDOWN(8)	      Linux System Administrator's Manual	   SHUTDOWN(8)

       shutdown	- bring	the system down

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

       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 immediately or after a specified
       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 edited, mail and news processing programs	 a  chance  to
       exit  cleanly,  etc.   shutdown	does  its  job	by signalling the init
       process,	asking it to change the	runlevel.  Runlevel 0 is used to  halt
       the  system, runlevel 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 ap-
       propriate entries for these runlevels in	the file /etc/inittab.

       -a     Use /etc/shutdown.allow.

       -t sec Tell  init(8)  to	wait sec seconds between sending processes the
	      warning and the kill signal, before  changing  to	 another  run-

       -k     Don't  really shutdown; only send	the warning messages to	every-

       -r     Reboot after shutdown.

       -h     Halt after shutdown.

       -n     [DEPRECATED] Don't call init(8) to do the	 shutdown  but	do  it
	      ourself.	The use	of this	option is discouraged, and its results
	      are not always what you'd	expect.

       -f     Skip fsck	on reboot.

       -F     Force fsck on reboot.

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

       time   When to shutdown.

	      Message to send to all users.

       The  time argument can have different formats.  First, it can be	an ab-
       solute time in the format hh:mm,	in which hh is the hour	(1 or  2  dig-
       its)  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.

       If  shutdown  is	 called	 with  a  delay,  it creates the advisory file
       /etc/nologin which causes programs such as login(1) to  not  allow  new
       user  logins. Shutdown removes this file	if it is stopped before	it can
       signal init (i.e. it is cancelled or something goes  wrong).   It  also
       removes it before calling init to change	the runlevel.

       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.  Af-
       ter that, the boot process should remove	/fastboot.

       The  -F	flag  means  `force fsck'.  This only creates an advisory file
       /forcefsck 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	to run
       fsck(1) with a special `force' flag so  that  even  properly  unmounted
       filesystems  get	 checked.   After that,	the boot process should	remove

       The -n flag causes shutdown not to call init, but to kill  all  running
       processes  itself.   shutdown will then turn off	quota, accounting, and
       swapping	and unmount all	filesystems.

       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
       authorized user is logged in on one of the virtual consoles.  If	 shut-
       down  is	 called	 with  the  -a argument	(add this to the invocation of
       shutdown	in /etc/inittab), it checks to	see  if	 the  file  /etc/shut-
       down.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/shutdown.allow  is
       one user	name per line. Empty lines and comment lines (prefixed by a #)
       are allowed. Currently there is a limit of 32 users in this file.

       Note that if /etc/shutdown.allow	is not present,	the -a argument	is ig-


       A lot of	users forget to	give the time argument and are then puzzled by
       the error message shutdown produces. The	time argument is mandatory; in
       90 percent of all cases this argument will be the word now.

       Init  can only capture CTRL-ALT-DEL and start shutdown in console mode.
       If the system is	running	the X window System, the  X  server  processes
       all  key	 strokes.  Some	 X11  environments make	it possible to capture
       CTRL-ALT-DEL, but what exactly is done with that	event depends on  that

       Shutdown	 wasn't	 designed to be	run setuid. /etc/shutdown.allow	is not
       used to find out	who is executing shutdown, it ONLY checks who is  cur-
       rently logged in	on (one	of the)	console(s).

       Miquel van Smoorenburg,

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

				 Juli 31, 2001			   SHUTDOWN(8)


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