There are several ways to upgrade from one Ubuntu release to another. This section gives an overview of the recommended upgrade method.
The recommended way to upgrade a Server Edition installation is to use the do-release-upgrade utility. Part of the update-manager-core package, it does not have any graphical dependencies and is installed by default.
Debian based systems can also be upgraded by using apt dist-upgrade. However, using do-release-upgrade is recommended because it has the ability to handle system configuration changes sometimes needed between releases.
To upgrade to a newer release, from a terminal prompt enter:
It is also possible to use do-release-upgrade to upgrade to a development version of Ubuntu. To accomplish this use the -d switch:
Upgrading to a development release is not recommended for production environments.
For further stability of a LTS release there is a slight change in behaviour if you are currently running a LTS version. LTS systems are only automatically considered for an upgrade to the next LTS via do-release-upgrade with the first point release. So for example 14.04 will only upgrade once 16.04.1 is released. If you want to update before, e.g. on a subset of machines to evaluate the LTS upgrade for your setup the same argument as an upgrade to a dev release has to be used via the -d switch.