Run Levels in Linux Operating system
Linux utilizes what is called "runlevels". A runlevel is a software configuration of the system that allows only a selected group of processes to exist. Init can run the system in one of eight runlevels. These runlevels are 0-6 and S or s. The system runs in only one of these runlevels at a time. Typically these runlevels are used for different purposes. Runlevels 0, 1, and 6 are reserved. For Redhat Linux version 6, the runlevels are:
0 - halt
1 - Single user mode
2 - Multiuser, without NFS (The same as 3, if you don't have networking)
3 - Full multiuser mode
4 - unused
5 - X11
6 - Reboot
1. level 0 : to halt the system, it reboots the systems again and again after login in 2. level1 :single user mode, this is a special mode in which only one use ie the super user mode in which limited syst...