Comment 14 for bug 579924

It looks like the Bacula version has changed between LTS versions, and in the change, the Bacula catalog
database changed format, so it has a new version number. Updating the Bacula catalog is done automatically
in rpms, but probably not in .debs. You must apply an update script that you can find in the <bacula>/src/cats directory
or in the <bacula>/updatedb directory. Sometimes the updatedb is package separately.

Actually, it looks like you need to apply two update scripts. One goes from 10 to 11 and the second from 11 to 12.
Of course, that all depends on the Bacula version you are starting from and the one you are going to. Normally,
if one upgrades each major bacula version (change in second digit of version), you will move only one database
version at a time.

You might ask packagers to include the update procedure automatically when installing new packages.
It is a lot more user friendly.