S Single user state (useful for recovery)
0 Go into firmware.
1 Put the system in system administrator mode. All local
file systems are mounted. Only a small set of essen-
tial kernel processes are left running. This mode is
for administrative tasks such as installing optional
utility packages. All files are accessible and no
users are logged in on the system.
2 Put the system in multi-user mode. All multi-user
environment terminal processes and daemons are
spawned. This state is commonly referred to as the
3 Extend multi-user mode by making local resources
available over the network.
4 Is available to be defined as an alternative multi-
user environment configuration. It is not necessary
for system operation and is usually not used.
5 Shut the machine down so that it is safe to remove the
power. Have the machine remove power, if possible.
6 Stop the operating system and reboot to the state
defined by the initdefault entry in /etc/inittab.