runlevel

RedHat

0: Halt
1: Single
2: Not used/User definable
3: Full multi-user NO display manager
4: Not used/User definable
5: Full multi-user with display manager (GUI)
6: Reboot

Debian

0: Halt
1: Single
2: Full multi-user with display manager (GUI)
3: Full multi-user with display manager (GUI)
4: Full multi-user with display manager (GUI)
5: Full multi-user with display manager (GUI)
6: Reboot