Run Levels

Linux Run Levels

0	Halt the system.
1	Single-user mode (for special administration).
2	Local Multiuser with Networking but without network service (like NFS)
3	Full Multiuser with Networking
4	Not Used
5	Full Multiuser with Networking and X Windows(GUI)
6	Reboot.

Where Does a Run Level Live?

/etc/rc0.d  Run level 0
/etc/rc1.d  Run level 1
/etc/rc2.d  Run level 2
/etc/rc3.d  Run level 3
/etc/rc4.d  Run level 4
/etc/rc5.d  Run level 5
/etc/rc6.d  Run level 6