This tutorial shows you all the steps necessary to upgrade from 12.04 Precise Pangolin to 14.04 Trusty Tahr. Important note: As a prerequisite you have to configure the Software & Updates manager properly. Launch the Software & Updates manager and choose the Updates tab. From the option "Notify me of a new Ubuntu version" select "For long-term support versions". If you select "For any new version", you will be upgrading to Ubuntu 12.10, if you select "never" you will not see the upgrade at all.