This post describes how I upgraded my Ubuntu (Hardy Heron) 8.04 server installation to (Intrepid Ibex) 8.10 from the command line.

First you’ll need to make sure you are running the latest packages

# sudo aptitude update
# sudo aptitude safe-upgrade

Then you will need to install the Ubuntu upgrade package

# sudo aptitude install update-manager-core

You can start the upgrade when the package is installed

# sudo do-release-upgrade

Then you just have to follow the on-screen instructions and answer the questions as they pop up. One thing to note is the fact that it is not suggested to perform the upgrade via a remote ssh connection. I have done earlier upgrades multiple times before without any problems, but I might just have been lucky.