Default init level is set in /etc/inittab.
$ cat /etc/inittab (to display the init levels)
Inside that file, you can note a line which will state the run level number like
id:5:initdefault: (indicating run level 5 which means that the system is running with x windows)
To find the current run level you can execute the following commands
$ who -r
run-level 5 2008-07-22 21:35 last=5
which indicates that the system is in run-level 5
Other option to find the run level is
$ /sbin/runlevel
N 5
To find out what sub processes are associated with each run level you can go to
$ cd /etc/rcN.d/ (Where N denotes the run level number)
For example
$ cd /etc/rc1.d/
$ ls -l
This will list symbolic links to various processes associated with run level 1.
