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Showing posts from April, 2010

Linux Run Levels

Runlevel Scripts Directory State
0 /etc/rc.d/rc0.d/ shutdown
1 /etc/rc.d/rc1.d/ Single user mode
2 /etc/rc.d/rc2.d/ Multiuser with no network services
3 /etc/rc.d/rc3.d/ Full Multiuser with no init 5 level services
4 /etc/rc.d/rc4.d/ Reserved for local use
5 /etc/rc.d/rc5.d/ GUI
6 /etc/rc.d/rc6.d/ Reboot
s or S Single user/Maintenance mode

Linux init Process

The init process is the last step in the boot procedure and identified by process id "1". Init is responsible for starting system processes as defined in the /etc/inittab file. Init typically will start multiple instances of "getty" which waits for console logins which spawn one's user shell process. Upon shutdown, init controls the sequence and processes for shutdown. The init process is never shut down. It is a user process and not a kernel system process although it does run as root.

System Processes:

Process ID Description
0 The Scheduler
1 The init process
2 kflushd
3 kupdate
4 kpiod
5 kswapd
6 mdrecoveryd