Run Levels

The Unix system environment gives various run levels which determine the several modes of system operation. The Run Levels under Unix, describes how the system gets begin up. After booting, the system begins as defined in ./etc/inittab. An instead to this method is assigning a special run level at boot time. The kernel passes any parameters, that it does not required, straightly to init. Run levels can be modify although the system is running, that as shown below.

# init S

The given syntax brings in a single user mode that is for administration and maintenance of the system. One can go to runlevel 2 again through the following

# init 2

Now all the essential programs are begins and users can log in and work with the system.