Runlevels (a Unix concept) are a way for system administrators to identify what services / daemons should be running at any given time. For example, runlevel 1 is generally used for doing maintenance that can only be done when there are no other users on the system, no network services are running, and there are minimal other services being run. This gives the maximum flexibility to the administrator to make configuration changes.

In my experience runlevel 3 is generally what a server runs within. It is configured for a text console but all network and services / daemons running. Then runlevel 5 is for a workstation or personal desktop, though it can also be used by servers if they want a graphical console. It generally adds a graphical login manager plus logins bring up a X11 desktop.

So why is it that Ubuntu (at least version 7.10) only configures two runlevels??? On Ubuntu, runlevel 1 is a single-user-administrator-maintenance mode and runlevel 2 is a full-on graphical login / desktop environment. What if, like I recently needed to do, you need to build a custom video driver or something like that? It is very paintful if you’re trying to download and compile drivers on a default install in this case since the only runlevel that is not using the video driver has no network and so many of the developer packages are not installed by default. You NEED network access. Switching back and forth via ‘init 1′ and ‘init 2′ is not very convenient. And that’s AFTER you figure out that you’re not in runlevel 5.

Can anyone explain why they did this?