/etc/rc.d/init.d/rc

/etc/rc.d/init.c/rc ist the main runlevel control script.

The script takes one argument: the new(?) runlevel that the system should go into.

This script is also the first script that is called by System V's boot process with the argument S (?).

The script sources /etc/sysconfig/rc.site to allow for cusomization.