Written by Robert -
Most current Linux distributions don't use runlevels anymore. Runlevels are used by the sysvinit system and it's being replaced in most distributions by systemd. Because a lot of servers and people that use Linux Mint still work with sysvinit, I've decided to write a small blog post about it. If you are looking for the runlevel system within systemd you would have to read the systemd.target manual. I will write an article about that in the future. A runlevel is simply a software configuration. You can assign a runlevel to a server and even create your own. There are several commonly used runlevels available within Linux systems. Runlevels can have different results in different distributions. Here are some common runlevels:
0 | Halt (standardized) 1 | Single user mode 2 | Debian default 3 | RedHat/Suse text mode 4 | Not commonly used except in Slackware 5 | RedHat/Suse Graphical mode, Unused in Slackware 6 | Reboot (standardized) S | Single user mode (standardized)
Now there are several reasons why you would want to use a different runlevel. One valid reason is to start a server in a text based mode. Most servers don't use a graphical interface for management. If you don't have the need for a graphical interface you can use the resources for more practical stuff, such as the task the server is assigned to do.
Viewing the current runlevel is different in different systems. For example, in a Debian based distribution I would use the 'runlevel' command but in an Arch or RedHat based distribution you can find the current runlevel in the /etc/inittab file.