-init initialization

#vi /etc/inittab



id –> it is 1-4 char. long identification char.

runlvele–> It represents the runlevel for which the action has to be taken.

If omitted, action will be taken for all the runlevels.

Action–> Represents the action to be taken for the specified runlevel.

(keywords like initdefault,sysinit etc…)

Process–>Represents the command or script to be run for the specified runlevel.

/etc/inittab main tasks


1. Determines default runlevel

2. Initializes the system initialization shell script (/etc/rc.d/rc.sysinit)

3. Initializes runlevel specific scripts in /etc/rc.d/rcx.d

(in rcx.d, x represents runlevel)

4. Traps certain key sequence (CTRL+ALT+DEL)

5. Defins UPS power fail/restore scripts

6. Starts gettys on virtual consoles

7. Starts X in run level 5.

Main tasks of /etc/rc.d/rc.sysinit


1.  Sets kernel parameters in /etc/sysctl.conf

2.  Sets system clock

3.  Loads keymap

4.  Enable swap partition

5.  Sets Hostname

6.  Root filesystem check & mount

7.  Add RAID devices

8.  Enable Disk quota

9.  Check & mount other filesystems

10. Cleans up stale locks & PID files