How to Switching or Changing Between Different Runlevels on Linux

In Linux, understanding and managing runlevels is a crucial skill for any webmaster or website administrator. Runlevels are essentially software configurations of a Linux system that permit only a certain group of processes to exist.

This tutorial will guide you through the process of switching or changing between different runlevels on a Linux system, providing you with the knowledge to manage your system’s processes more effectively.

Understanding Runlevels

In Linux, runlevels 0, 1, and 6 are typically the same and reserved for specific purposes:

  • 0 – Halt
  • 1 – Single mode
  • 6 – Reboot

On the other hand, runlevels 2, 3, 4, and 5 are used for:

  • 2 – Multi-User Mode
  • 3 – Multi-User Mode with Networking
  • 4 – Not used/User-definable
  • 5 – Start the system normally with appropriate display manager (with GUI)

Switching Between Runlevels

There are two methods to switch or change between different runlevels on Linux. These steps have been tested on CentOS 6.2.

Method 1: Changing Runlevel Temporarily Without Reboot

To change the runlevel immediately without a reboot, you can use the init command. For instance, if you are currently in the default runlevel 3 and want to switch to runlevel 1 (which will enter single user mode), execute the following command:

[root@centos62 ~]# init 1

To shut down the system, execute the following command:

[root@centos62 ~]# init 0

To reboot the system, execute the following command:

[root@centos62 ~]# init 6

Please note that these commands are not permanent and the system will return to the default runlevel after a reboot.

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Method 2: Changing the Runlevel Permanently

To change the runlevel permanently, you need to edit the /etc/inittab file. Here’s how to do it:

[root@centos62 ~]# vi /etc/inittab

Assume the default runlevel is 3:

[root@centos62 ~]# id:3:initdefault:

Change the initdefault to 5 as below:

[root@centos62 ~]# id:5:initdefault:

This change will make the system boot into runlevel 5 by default.

Commands Mentioned

  • init 1 – Switches the system to single user mode
  • init 0 – Shuts down the system
  • init 6 – Reboots the system
  • vi /etc/inittab – Opens the inittab file for editing


Understanding and managing runlevels is a fundamental skill for any Linux user, especially for webmasters and website administrators. Whether you’re operating on a dedicated server, a VPS server, or utilizing cloud hosting or shared hosting, being able to switch between different runlevels can help you manage your system’s processes more effectively.

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This tutorial has provided you with two methods to change runlevels, either temporarily without a reboot or permanently. Remember, the ‘init’ command is your friend when it comes to changing runlevels on the fly, and the /etc/inittab file is where you can set the default runlevel for your system.

By mastering these skills, you can ensure that your Linux system is always operating in the mode that best suits your current needs. Whether you’re troubleshooting, performing maintenance, or optimizing performance, understanding runlevels is a key piece of the puzzle.

If you’re interested in learning more about specific servers, you can check out our detailed guides on Apache, Nginx, and LiteSpeed.


  1. What is a runlevel in Linux?

    A runlevel in Linux is a mode that defines the specific processes that the system runs. Different runlevels are used for different purposes, such as halting the system, rebooting, single-user mode, multi-user mode, and more.

  2. How can I change the runlevel without rebooting the system?

    You can change the runlevel without rebooting the system by using the ‘init’ command followed by the number of the desired runlevel. For example, ‘init 1’ will switch the system to single user mode.

  3. How can I make the runlevel change permanent?

    You can make the runlevel change permanent by editing the /etc/inittab file. In this file, you can change the ‘initdefault’ value to the number of the desired runlevel.

  4. What is the purpose of different runlevels?

    Different runlevels serve different purposes. For example, runlevel 0 is used to halt the system, runlevel 1 is for single-user mode, runlevel 6 is for rebooting, and runlevels 2, 3, and 5 are for multi-user modes with varying levels of networking and graphical interfaces.

  5. What is the ‘init’ command in Linux?

    The ‘init’ command in Linux is used to change the runlevel of the system. It can be used to switch between different modes, such as single-user mode, multi-user mode, reboot, and halt.


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