What is a partial upgrade and when is it necessary?

See the information provided on this web site:

• https://wiki.ubuntu.com/U%2B1/partial_upgrade

Summary

If you use Update Manager to upgrade your packages, and it offers to do a Partial Upgrade do not accept it without thoroughly checking what packages it offers to remove, upgrade and install. If you do, you will most likely end up removing packages that shouldn't be removed, and waste time and effort repairing your testing installation and asking for assistance.

Most Partial Upgrade situations occur due to package archive inconsistencies, which will typically be resolved within a few hours. If your package manager is confused, and so are you, simply wait and hold off the updates until things settle down.

Short Version

Due to the fact that uploads to the repositories of the active development branch are asynchronous and uncoordinated, dependencies of certain packages may arrive later than the dependent package. This causes package management tools such as Update Manager, which are mainly meant to be used with stable releases of Ubuntu where the package archive is always consistent, to interpret the situation as requiring a dist-upgrade to install new packages and/or repair packages in a reqreinst (requires reinstallation) state. What Update Manager performs when doing a "Partial Upgrade" is a dist-upgrade.

When testing development releases, most of the time, a Partial Upgrade is undesired. The situations where it's needed are limited to new packages obsoleting old ones (as in the case of the software-center package replacing software-store) and package removals from the archive.

Do not assume that since you're running a development release, a Partial Upgrade is necessarily warranted.