Terminate all processes and shut down (or reboot) the system.
shutdown [options] time [messages]
-t seconds specifies the time between the message and the kill signal.
-h halts the system after terminating all the processes.
-r reboots the system after terminating all the processes.
-f performs a fast reboot.
-k sends warning messages but does not shut down the system.
-c cancels a shutdown that’s in progress.
The shutdown command (the full pathname is /sbin/shutdown) brings down the Linux system in an orderly way. You must specify a time when shutdown begins; use the keyword now to shutdown immediately. You must be logged in as root to run the shutdown command.