Upgrade from Ubuntu 9.04 on a desktop system
First,press Alt+F2 and type in “update-manager -d” (without the quotes) into the command box.
Update Manager should open up and tell you: New distribution release ’9.10′ is available. Click Upgrade and follow the on-screen instructions.
Upgrade from Ubuntu 9.04 on a server system
First,install the update-manager-core package if it is not already installed.
Edit /etc/update-manager/release-upgrades and set Prompt=normal; launch the upgrade tool with this command:
sudo do-release-upgrade -d
and follow the on-screen instructions.