Sometimes you install this and that PPA (Personal Package Archive) to get the latest versions of a given program, library, whatever. And then, after running apt-get upgrade, your system breaks. How do you downgrade those packages that you’ve just installed? Removing the PPA from the sources.list isn’t going to help. Neither is trying to manually re-install the old packages – ie. you’ll likely end up with broken dependencies and an overall even more broken system.
There was a discussion in the Ubuntu lists where they explained why Ubuntu doesn’t support downgrading of packages out-of-the-box. However, the very last reply to that thread shed some light and offered a solution. Ironically, a software package installed in the very same PPA I am about to remove – PPA-Purge.
Usage is in fact quite simple and for me, it worked flawlessly. Ubuntu offers a single line solution to install a PPA: apt-add-repository ppa-name/here. PPA-Purge offers a likewise simplistic approach: ppa-purge ppa-name/here.