shutdown -t 0 -r -f

Possible flags:

• -s :: shut down
• -r :: restart
• -l :: log off
• -h :: hibernate
• -i :: “Interactive mode”. Instead of performing an action, it displays a GUI dialog
• -a :: aborts a previous shutdown command
• -f :: forces programs to exit. Prevents the shutdown process from getting stuck
• -t <seconds> :: sets the time until shutdown. Use -t 0 to shutdown immediately
• -c <message> :: adds a shutdown message. The message will end up in the Event Log
• -y :: forces a “yes” answer to all shutdown queries