Tip 13: Shutdown and power off

Linux, like most other operating systems, must be shutdown in a specified manner. You can't turn the power
off on a computer running Linux, or you may lose some data.
Here are the steps that need to be done when you want to shutdown:
· The operating system needs to stop all the running processes and logout the users.
· Various servers need to be shutdown in a proper way.
· All the mounted file systems need to be unmounted safely and unwritten data need to be stored
on the disk.
The system can then be turned off safely.
To accomplish all these tasks, the shutdown command exists. That command has a lot of options, and you
should explore them before trying anything at random. Another way to shutdown a Linux system is to set the
runlevel to 0, the default shutdown level, with the init program.