Shutdown

In UNIX, the shutdown command can be used to shut down (turn off) or reboot a computer.

One commonly issued form of this command is shutdown -h now, which will shut down a system immediately.

Another one is shutdown -r now to reboot.

Unlike in many other operating systems, you may also specify an exact time or a delay: shutdown -h 20:00 will turn the computer off at 8:00 PM, and shutdown -r -t 60 will automatically reboot the machine in 60 seconds (one minute) of issuing the command.

The complete syntax from the Linux version of the command is as follows.

Usage:    shutdown [-akrhfnc] [-t secs] time [warning message]
                  -a:      use /etc/shutdown.allow
                  -k:      don't really shutdown, only warn.
                  -r:      reboot after shutdown.
                  -h:      halt after shutdown.
                  -f:      do a 'fast' reboot (skip fsck).
                  -F:      Force fsck on reboot.
                  -n:      do not go through "init" but go down real fast.
                  -c:      cancel a running shutdown.
                  -t secs: delay between warning and kill signal.
                  ** the "time" argument is mandatory! (try "now") **

Please note that you must be the superuser (usually root) to shut the system down, for fairly obvious reasons.

See also

• Halt, Reboot – equivalent to shutdown -h now and shutdown -r now respectively.