You have more than one command option that you can use. The best command is this, executed as root:
shutdown -y -i5 -g0
This will immediately shut the system down. You can also use the older command that still works:
You can even use:
If you are trying to reboot the system as opposed to turning it off, you could use:
shutdown -y -i6 -g0
So many commands to do the same thing… almost seems silly.
Ref: How to Geek