run levels and runlevel

This covers the concept of run levels and the utility: runlevel

run levels

run level

defines what system services are running
7 levels available, from 0 to 6
default server system runlevel: 3
default desktop system runlevel: 5
after the kernel, the init process is the first process to run (PID 1) and it behaves based on the current run level, which is set in the file /etc/inittab ( WebHome )

runlevel	description
0	shut down the system
1	single-user mode
2	local multiuser with networking, but without network service (like NFS)
3	full multiuser with networking, console login only
4	not used / user defined
5	full multiuser with networking, console login and X Windows GUI
6	reboot the system

Note that run levels may change slightly from one Linux distribution from another.

You can see what services should be running by level by using the command chkconfig

runlevel command will tell you what the current run level is.

[user@acc ~]$ /sbin/runlevel
N 3

Here runlevel states that the current run level is 3.

See the following for more information on these topics:

Run Levels

-- RobertSajan - 03 Oct 2008