Linux Run-Levels

When you boot a computer running Linux, it will boot into a default runlevel (this is usually level 3 or level 5). There are six different runlevels most Linux distributions use, the following runlevels are defined by default under Red Hat Enterprise Linux:

	0 - Halt the system
	1 - Single-user text mode
	2 - Not used (user-definable)
	3 - Full multi-user text mode (no display manager)
	4 - Not used (user-definable)
	5 - Full multi-user with graphical mode (GUI)
	6 - Reboot the system

Run levels 1 and 2 are not often used.
Most Linux systems run in runlevel 3 or 5.
Most desktop Linux systems boot into runlevel 5 by default and the user is greeted by a graphical login prompt.
Most server Linux systems boot into runlevel 3 by default and the user is greeted by a text-mode login prompt.

Useful Links

For further information see the following links. For the full story consult the manual (man) pages for your distribution.