Linux Runlevels Explained

October 2, 2019 Liquid Web

In this video, we will explain what a runlevel is, what each Linux runlevel is for, and an example of how to manage a service using a runlevel. 

Commands used:
Level 0 is for shutting down the system. Nothing runs and the system just halts all functions.

Level 1 is Single-User Mode, which means only root has access to the system, the network access, and other non-vital services won't run. Generally, this is more of a recovery mode than something that would be used regularly. It can be used to reset the root password if you get locked out.

Level 2 is Multi-User Mode, so basically the same as level 1, but it allows other users to log in as well.

Level 3 is Multi-User Mode with Networking. This is how most servers run as it allows external communication but doesn't use a graphical user interface.

Level 4 is Undefined. It's for allowing custom user runlevels to be configured if there is a specific configuration that needs to be used regularly.

Level 5 Is X11 Mode, which means it has everything level 3 has plus the GUI. So Linux desktops and home users would generally boot into this mode by default.

Level 6 is for rebooting the system. So like level 0 you wouldn't boot into this mode, but the system will switch to this mode when the reboot process in initiated.

chkconfig --list 
chkconfig memcached off
chkconfig memcached on

The related article for this article can be found here: https://www.liquidweb.com/kb/linux-runlevels-explained/https://www.liquidweb.com/kb/

For more information about this and other topics, visit us at https://www.liquidweb.com/kb/ or
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Video by: Alex Gorzen

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