Q: Why do I get "some packages could not be authenticated" when upgrading from Lucid to Precise?

Answer

When upgrading Debathena from Lucid (Ubuntu 10.04) to Precise (Ubuntu 12.04), the upgrade may fail with the error "Some packages could not be authenticated", and it may display a list of all debathena packages.

This is caused by a bug in the "APT" software which causes it to download some metadata in one format while attempting to verify it as though it were in the older format. The easiest way to workaround it is to (as root) create the following file:

/etc/update-manager/release-upgrades.d/unauth.cfg

with the following content:

[Distro]
AllowUnauthenticated=yes

Then re-run the upgrade. We strongly encourage you to remove that file once you have upgraded to Precise.