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RedHat 9 (Linux i386) - man page for shutdown (redhat section 8)

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.  shut-
       down does its job by signalling the init process, asking it to change the runlevel.   Run-
       level  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 appropriate entries for these runlevels  in	the  file

       -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 runlevel.

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

       -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 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.

       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.  After 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 /forcefsck.

       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  cre-
       ating  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/init-
       tab),  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/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 ignored.


       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 argu-
       ment 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 environment.

       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 currently logged in  on  (one  of  the)  con-

       Miquel van Smoorenburg, miquels@cistron.nl

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

					  Juli 31, 2001 			      SHUTDOWN(8)

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