TECH SOLUTION

TECH SOLUTION

Saturday, 19 October 2013

INIT PROCESS IN LINUX



THE INIT PROCESS


1.     The init process is the first non-kernel process that is started, and, therefore, it always gets the process ID number of 1.

2.     init reads its configuration file, /etc/inittab, and determines the runlevel where it should start.



3.     Essentially, a runlevel dictates the system’s behavior.


4.     Each level (designated by an integer between 0 and 6) serves a specific purpose.

5.     A runlevel of initdefault is selected if it exists; otherwise, you are prompted to supply a runlevel value.




Run Level ID
Description

0
Halt the system      

1
Enter single-user mode

2
Multiuser mode, but without Network File System (NFS)

3
Full multiuser mode (normal)

4
Unused

5
Same as runlevel 3, except using an X Window System login rather than a text-based login

6
Reboot the system


6.     When it is told to enter a runlevel, init executes a script, as dictated by the /etc/ inittab file.

7.     The default runlevel that the system boots into is determined by the initdefault entry in the /etc/inittab file.

If, for example, the entry in the file is :- id:3:initdefault
--> This means that the system will boot into runlevel 3. 
-->But if, on the other hand, the entry in the file is id:5:initdefault:, 
--> This means the system will boot into runlevel 5, with the X Window subsystem running with a graphical login screen.

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