The init command will allow you to change the current runlevel, and for a shutdown, that value is 0. Here is an example:
[root@bigboy tmp]# init 0
Fedora also has a shutdown command which can also be used to the same effect. It often prompts you as to whether you are sure you want to execute the command, which can be avoided with the -y switch. The -h switch forces the system to halt, and the first argument tells it how long to wait before starting the procedure, in this case 0 minutes. You can also specify shutting down at a specific time of the day; please refer to the man pages for details. Another advantage of the shutdown command is that it warns people that the shutdown is going to occur.
[root@bigboy tmp]# shutdown -hy 0 Broadcast message from root (pts/0) (Sat Nov 6 13:15:27 2004): The system is going down for system halt NOW! [root@bigboy tmp]#