What is Run Level in Linux?

Run-level is a system state on  how the process is starting and what process to run ,which service to enable and disable while booting is decided by the Run-level program.While booting process after the kernel has started the init program it reads the /etc/inittab file where  the default run-level entry saved. and then it starts all the services.

There are totally seven run-levels available in UNIX ,according to the OS  the run-level number may vary.

Types of Run-levels:

In Linux by default it boots either Run-level 3 or run-level 5.You can also modify or switch to different run-levels as per the  needs.

To check the current Run Level settings:
#who  -r

r=Run-level

Sample output for the above command would be

To check the current and previous Run-level details
#runlevel

Sample output for the above command would be

n

In the above output ,“N” indicates the run-level has not been changed since the system was booted.“3” is the current run-level

To change the default Run-level 

/etc/inittab file holds the default run-level entry,open this file with the vi editor and change the run-level number to your desired one as follows,

Here am going to change the run-level from 3 to run-level 5

#vi /etc/inittab

Modify the line as follows

remove 5 and add 3 in the above line,after update reboot the system to login n to the new run-level

To reboot use the following command
#init 6

I hope you find this guide useful

More good stuffs to come,Stay tuned!!!!

Mail me your queries to vasanth@linuxvasanth.com

 

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About Author:

Hello readers! Let me introduce my self first. My name is Vasanth Nirmal Singh J S having 9+ years of experience in IT on all flavours of Unix operating systems ,Storage's and many more .. I would like to share my technical experience i have come across - can be help to other people. So in this blog, I'll post my thoughts related to ITIS. I'll share experiences that I've had while working in different environments. You can expect content related to Unix,Solaris,Linux,EMC Storeages,HP-UX and many others. I hope this blog can be useful for you! Your comments will be appreciated!

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