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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 sig-nal signal
             nal 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 (indicat-ing (indicating
             ing 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 speci-fied. specified.
             fied.

     warning-message
             Any other arguments comprise the warning message that is broadcast 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 starting at ten hours before shut-down, shutdown,
     down, 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 respec-tively respectively
     tively 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 indeterminate 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 ven-dor, vendor,
     dor, should they encounter an issue with this functionality.

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 com-patibility. compatibility.
     patibility.

HISTORY
     The shutdown utility appeared in 4.0BSD.

BSD                            December 11, 1998                           BSD

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