SHUTDOWN(8)               BSD System Manager's Manual              SHUTDOWN(8)

NAME
     shutdown -- close down the system at a given time

SYNOPSIS
     shutdown [-] [-h [-u] | -r | -s | -k] [-o [-n]] time
              [warning-message ...]

DESCRIPTION
     The shutdown utility provides an automated shutdown procedure for super-
     users to nicely notify users when the system is shutting down, saving
     them from system administrators, hackers, and gurus, who would otherwise
     not bother with such niceties.

     The following options are available:

     -h      The system is halted at the specified time.

     -k      Kick everybody off.  The -k option does not actually halt the
             system, but leaves the system multi-user with logins disabled
             (for all but super-user).

     -n      If the -o is specified, prevent the file system cache from being
             flushed by passing -n option to halt(8) or reboot(8).  This
             option should probably not be used.

     -o      If -h or -r is specified, shutdown will execute halt(8) or
             reboot(8) instead of sending a signal to launchd(8).

     -r      The system is rebooted at the specified time.

     -s      The system is put to sleep at the specified time.

     -u      The system is halted up until the point of removing system power,
             but waits before removing power for 5 minutes so that an external
             UPS (uninterruptible power supply) can forcibly remove power.
             This simulates a dirty shutdown to permit a later automatic power
             on. OS X uses this mode automatically with supported UPSs in
             emergency shutdowns.

     time Time is the time at which shutdown will bring the system down and
             may be the word now (indicating an immediate shutdown) or specify
             a future time in one of two formats: +number, or yymmddhhmm,
             where the year, month, and day may be defaulted to the current
             system values.  The first form brings the system down in number
             minutes and the second at the absolute time specified.

     warning-message
             Any other arguments comprise the warning message that is broad-
             cast to users currently logged into the system.

     -       If `-' is supplied as an option, the warning message is read from
             the standard input.

     At intervals, becoming more frequent as apocalypse approaches and start-
     ing at ten hours before shutdown, warning messages are displayed on the
     terminals of all users logged in.

     At shutdown time a message is written to the system log, containing the
     time of shutdown, the person who initiated the shutdown and the reason.
     Corresponding signal is then sent to launchd(8) to respectively halt,
     reboot or bring the system down to single-user state (depending on the
     above options).

     A scheduled shutdown can be canceled by killing the shutdown process (a
     SIGTERM should suffice).

SIGTERM TO SIGKILL INTERVAL
     Upon shutdown, all running processes are sent a SIGTERM followed by a
     SIGKILL.  The SIGKILL will follow the SIGTERM by an intentionally inde-
     terminate period of time.  Programs are expected to take only enough time
     to flush all dirty data and exit.  Developers are encouraged to file a
     bug with the OS vendor, should they encounter an issue with this func-
     tionality.

SEE ALSO
     kill(1), login(1), wall(1), halt(8), launchd(8), reboot(8)

BACKWARD COMPATIBILITY
     The hours and minutes in the second time format may be separated by a
     colon (``:'') for backward compatibility.

HISTORY
     The shutdown utility appeared in 4.0BSD.

BSD                            December 11, 1998                           BSD