I recommend backing up conf files before upgrading.

1. Update your repository <br />

sudo aptitude update

1. Install update-manager-core if it is not already installed:<br />

sudo aptitude install update-manager-core

1. Edit the file /etc/update-manager/release-upgrades <br />

Make sure prompt is set to normal (Prompt''normal)

1. Launch the upgrade tool:<br />

sudo do-release-upgrade

1. Follow the on-screen instructions.

– Main.FredPettis - 18 May 2009