Run Levels in RHEL6

The SysV init runlevel system provides a standard process for controlling which programs init launches or halts when initializing a runlevel.

The configuration files for SysV init are located in the /etc/rc.d/ directory. Within this directory, are the rc, rc.local, rc.sysinit and optionally, the rc.serial scripts as well as the following directories.

The init.d/ directory contains the script used by the /sbin/init command when controlling services. Each of the numbered directories represent the six default run levels configured by default under RHEL.

Runlevels are a state, or mode, defined by the services listed in the SysV /etc/rc.d/rc<x>.d/ directory, where <x> is the number of the runlevel.

The following runlevels are defined by default for RHEL.

Runlevel	Description
0	Halt
1	Single-user text mode
2	Not Used ( user-definable)
3	Full multi-user text mode
4	Not used (user-definable)
5	Full multi-user graphical mode
6	Reboot

Identify current run level:

Use the 'runlevel" command to get the previous and current runlevel of the system.

Changing the current level:

Use the following command to change the current runlevel.

#init <new_runlevel>

Changing the default runlevel:

Use any text editor to open the file /etc/inittab. Edit the last line of this file and change the number after id: to the desired runlevel.