In Unix-based computer operating systems, init (short for initialization) is the first process started during booting of the computer system. Init is a daemon process that continues running until the system is shut down. The First program that is run under the kernel is init. This program is always processes 1. The linux kernel can be told which program to use as init by passing the init=boot parameter. If this parameter is not specified then the kernel will try to excute ‘/sbin/init’,’/etc/init’,’/bin/init’ & ‘/bin/sh’.
The init process is identified by process id “1”.
Init is Responsible for starting system processess as defined in the /etc/inittab file.
Init typically will start multiple instances which waits for console logins which spawn ones user shell process.
Upon shutdown, init controls the sequence & Procssess for shutdown.
The first thing the kernl does is to execute init program.
Init is the root of all processes excuting on linux.
The first processes that init starts is a script /etc/rc.d/rc.sysinit
Based on the appropriate run-level, scripts are executed to start various processes to run the system and make it functional.