Terminate all processes and reboot the system (you must log in as root).
-n reboots the system without flushing out in-memory buffers to disk.
-f forces a halt without calling the /sbin/shutdown command.
-i shuts down all network interfaces before rebooting the system.
The reboot command lets the super user (root) terminate all processes and reboot the system. The reboot command invokes /sbin/shutdown with the -r option.