0
0 - Halt Mode
All Processes terminated; orderly halt (Do not set initdefault)
1
1 - Single User Mode
Used to perform administrator tasks on system
2
2 - Multi User Mode
Allows Users to access the system; limited network services
3
3 - Full multi user mode
Same as multi user mode, but includes network services
4
4 - User Defined mode
Not specified by system. Universally defined and customizeable
5
5 - X11
Default for Linux, multiuser, network services and X-windows display manager (X11)
6
6 - Reboot Mode
All processes terminated; system is gracefully rebooted