Changing Run Levels

On production environment normal run level 3 is used and it get rarely changed.
Runlevel and usage:

• 0 — Halt
• 1 — Single-user mode
• 2 — Not used (user-definable)
• 3 — Full multi-user mode
• 4 — Not used (user-definable)
• 5 — Full multi-user mode (with an X-based login screen)
• 6 — Reboot

Check run level using :-
#who -r or #runlevel

Change run level using:-
#telinit 5 or
open file
#emacs /etc/inittab
Look for the default runlevel called initdefault which look like as follows:
id:3:initdefault:
Replace run level x with y (where x is current run level and y you want to set).

Set services in run level using :
#ntsysv or
#chkconfig or
#serviceconf