Quite simply a “runlevel” is a state in Ubuntu, which is neither “On” or “Off” but a state in between the two.

A “runlevel” exists in Ubuntu because, unlike other operating systems, Ubuntu allows for different states of operation. These “runlevels” influence which processes are loaded at bootup on a Ubuntu system. These processes being controlled are usually very important processes, such as mounting HDDs on boot or sending output to the input of your monitor.

 

By default all boot processes will be run automatically at boot, although by editing the file that controls the “runlevels” you are able to decide exactly which processes start and in which order.

 

There are several “runlevels” in Ubuntu. They are listed below:

Runlevel Number Runlevel Function
Runlevel 0 This runlevel is also known as “halt” in that it is used to shutdown Ubuntu.
Runlevel 1 This runlevel is unique in that it boots to a shell prompt which will allow a login, although this login must be to the root account only as no other account logins are accepted. This is used for root changes to the system when a graphical interface must not be used, such as installing graphics drivers or updating some system files.
Runlevel 2 This is the regular runlevel for Ubuntu and is used by default.
Runlevel 3 This particular runlevel is not used in Ubuntu, although it is used in an array of other Linux distributions.
Runlevel 4 This particular runlevel is not used in Ubuntu, although it is used in an array of other Linux distributions.
Runlevel 5 This particular runlevel is not used in Ubuntu, although it is used in an array of other Linux distributions.
Runlevel 6 This runlevel is used to restart the Ubuntu system.

I hope that this piece has informed you on the uses of runlevels on Ubuntu, Kubuntu and Xubuntu. Enjoy your newfound Linux knowledge.

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