1) Shutdown the system immediately.
# shutdown -h now
2) Reboot the system now
# shutdown -r now
3) or you can use reboot command
# reboot
4) Delayed shutdown by 2 minutes
# shutdown -h 120
5) Shutdown at 10:00PM
# shutdown -h 22:00
6) Requests that the system be powered off explicitly.
# shutdown -P now
7) Force the filesystem check during reboot
# shutdown -Fr now
In CentOS/RHEL 6, with new Upstart utility both poweroff and halt commands pointed to reboot command. These programs allow a system administrator to reboot, halt or poweroff the system.
# shutdown -P now
is quite equal to
# poweroff
and
# shutdown -r now
is quite equal to
# reboot
