Keep the following in mind when you shut down a system:
Use either the shutdown or the init command to shut down a system. Both commands perform a clean system shutdown, which means all system processes and services are terminated normally.
You need to be the root role to use the shutdown and init commands.
Both the shutdown and init commands take a run level as an argument.
The three most common run levels are as follows:
Run level 3 – All system resources are available and users can log in. By default, booting a system brings it to run level 3, which is used for normal day-to-day operations. This run level is also known as the multiuser state, with NFS resources shared.
Run level 6 – Shuts down the system to run level 0, and then reboots the system to a multiuser level with SMB or NFS resources shared (or whatever run level is the default in the inittab file).
Run level 0 – The operating system is shut down, and it is safe to turn off power. You need to bring a system to run level 0 whenever you move a system, or add or remove hardware.
Run levels are fully described in How Run Levels Work.