shutdown - bring the system down
[SYNOPSIS] shutdown OPTION TIME MESSAGE
-h Halt or poweroff after shutdown
# shutdown -h now
-r Reboot after shutdown
# shutdown -r +10
-f Skip fsck on reboot
# shutdown -rf +20 "This System will shutdown soon"
-k Don’t really shutdown; only send the warning messages to everybody
# shutdown -k now
-c Cancel an already running shutdown
# shutdown -c