THis is more of a tip to shutdown linux (arch linux) immediately from the command line. Generally issuing the command "shutdown" will notify all connected users and then will go for shutdown after a while. This might not be necessary sometimes as you would wish to shutdown immediately. To do so type the following command
shutdown -H -time "now", to shutdown.
Note : If you have configured to login in single user mode always, then just issuing "shutdown" should be necessary.