To upgrade from Ubuntu 10.04 to 11.04, you need to perform the steps listed below:
1. Install update-manager-core if it is not already installed:
sudo apt-get install update-manager-core
2. vi /etc/update-manager/release-upgrades and set Prompt=normal
3. Run sudo do-release-upgrade
4. Follow the prompts and after the install completes, you will be prompted to reboot your server/desktop.
5. When the server comes back up, you can confirm the version by typing cat /etc/lsb-release
