Based on the fact, that Ubuntu 9.04 was announced today, it is a good idea to explain how to upgrade every Ubuntu Version using the command line.

  1. sudo apt-get install update-manager-core
  2. verify /etc/update-manager/release-upgrades to use LTS or Normal based on your preferences
  3. sudo do-release-upgrade

After that, follow the messages on the screen to upgrade your system to the newest Ubuntu Version.