SHUTDOWN linux command manual

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 speci-
       fied 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 appropriate entries for these runlevels in the file /etc/init-

       -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
       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

       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
       shutdown 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


       A lot of users forget to give the time argument and are  then  puzzled
       by  the  error  message shutdown produces. The time argument is manda-
       tory; 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)