The Boot Process after load kernel with Redhat

Summary:

step one:call /etc/inittab #this is the first file called by kernel

step two:call /etc/rc.d/rc.sysinit

step three:call the correspond to runlevel scripts

Detail see below:

The Boot Process
The init process is the first program called by the kernel. This process in turn runs
/etc/rc.d/rc.sysinit, which performs a number of tasks, including network configuration,
keymaps, mounting partitions, and setting the host name. The init process then
determines which runlevel it should be in by looking at the initdefault entry in
/etc/inittab. A runlevel is defined as a group of activities. For example, the entry:
id:5:initdefault:
shows a default starting point in runlevel 5. Next, init starts the appropriate scripts
associated with runlevel 5, from the /etc/rc.d directory. That directory includes the
following subdirectories:
init.d
rc0.d
rc1.d
rc2.d
rc3.d
rc4.d
rc5.d
rc6.d
If the default runlevel is 5, init will look in /etc/rc.d/rc5.d and run each “kill” and
“start” script it finds in that directory. A kill script is any file or symbolically linked
file with a name that begins with a “K.” Likewise, start scripts start with “S.” If you
run an ls -l command in this directory, you’ll see only symbolic links to the actual
scripts in /etc/rc.d/init.d.