Tell me various runlevels in linux OS
Following are the run-levels which you could refer :
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
If you use a command line login screen, then you are in runlevel 3.
If you use a graphical login screen, you are operating in runlevel 5.
The default runlevel can be changed by editing the /etc/inittab file.
It contains a line near the top of the file similar to the following:
Change the number in this line to the desired runlevel.
You will have to reboot the system for the changes to take effect.