Terminate all processes and halt the system (you must log in as root).
-n does not flush out in-memory buffers to disk before halting the system.
-f forces a halt without calling the /sbin/shutdown command.
-i shuts down all network interfaces before halting the system.
The halt command lets the super user (root) terminate all processes and halt the system. The halt command invokes /sbin/shutdown with the -h option.