How to upgrade Ubuntu 11.04 to 12.04

apt-get update updates the package manager cache of what packages are available. apt-get upgrade upgrades packages that are already installed to newer versions. Neither upgrades to a new release. For that you need to either use the gui update manager, or do-release-upgrade.

You also can not skip releases except from LTS to LTS, so you must first upgrade to 11.10, then to 12.04.

You can force to upgrade the release with:

sudo do-release-upgrade

From 11.04, it will upgrade to 11.10 I think and you do it again to upgrade to 12.04.

I've been using do-release-upgrade on multiple machines through several Ubuntu versions and I've been really happy with the results. A few additional steps have made it even more useful for me.

I often am upgrading remotely and would like to hop into the box being upgraded and check on the progress. You can use "screen" or, my preference, "tmux" to disconnect a remote session then "tmux a" to re-attach and see what's going on.

Just one more point worth mentioning; I frequently am an early adopter using the new version before it's released. Use "do-release-upgrade -d" to upgrade to a development version of Ubuntu.

I have upgraded from 10.04 to 12.04.1 LTS with no problems, simple preferences, and some of the settings may need to be reintegrated; however, for the most part, the OS upgrades without any problems, so as long as you have connection to the internet for when the installer needs something from the net.