Dist-upgrading Ubuntu when the PPA version of a package is newer?

April 25, 2012 8:54 AM

Upgrading Ubuntu: I am planning to finally dist-upgrade my mythbuntu 10.10 box which has fallen out of official support. I probably will take 3 steps to get it up to 12.04 LTS, but this question is just about the first step. What happens during a dist-upgrade if I have a ppa-sourced package that is newer than the new distribution?

I am currently using the "Team XBMC" maverick PPA, to get the latest version of XBMC. So I am running XBMC 11 on my box right now.
If I do a dist-upgrade from 10.10 to 11.04, what will happen to my version of XBMC?

Will it remain at version 11 from the PPA?
Will it "downgrade" to the standard version included with natty until I reinstate the PPA?
Or will I get a scary error message mid-upgrade where it won't let me upgrade anything?

I just want to make sure that this part will go smoothly before I even begin the upgrade process.

If the upgrade process will complain at me, then what should I do before upgrading?


(I also asked this over on superuser.com but haven't gotten any eyeballs on the question there.)

posted by jozxyqk to Computers & Internet (6 answers total)

Best answer: Packages are never downgraded. The version number reigns supreme, regardless of source (discounting "pinning" -- discussed below).

if the new Ubuntu has a version of the package that sorts higher than what is in the other archive you're using, your computer will download it and install it. If new Ubuntu has a lesser version number, it will not.

You may change the sources line in /etc/apt/sources.list and run "apt-cache policy xbmc" (after "apt-get update" of course) to see what the system expects to do on "apt-get upgrade".

If you dislike what it will do, you may investigate "pinning APT" to various criteria to keep the versions you want, so that version numbers are not even considered in other archives.
posted by cmiller at 9:12 AM on April 25, 2012 [1 favorite]

Response by poster: I'm not sure I understand the output of the apt-cache command.

Here is the output:

xbmc:
Installed: 2:11.0~git20120321.14feb09-0ubuntu1~ppa1~maverick
Candidate: 2:11.0~git20120321.14feb09-0ubuntu1~ppa1~maverick
Version table:
*** 2:11.0~git20120321.14feb09-0ubuntu1~ppa1~maverick 0
500 http://ppa.launchpad.net/team-xbmc/ppa/ubuntu/ maverick/main amd64 Packages
100 /var/lib/dpkg/status
2:10.1~ppa1~maverick 0
500 http://ppa.launchpad.net/team-xbmc/ppa/ubuntu/ maverick/main amd64 Packages

But.. I thought that PPA sources were "commented out" during a dist-upgrade. If I temporarily remove the PPA from my sources, then I get this output from the apt-cache command:

xbmc:
Installed: 2:11.0~git20120321.14feb09-0ubuntu1~ppa1~maverick
Candidate: 2:11.0~git20120321.14feb09-0ubuntu1~ppa1~maverick
Version table:
*** 2:11.0~git20120321.14feb09-0ubuntu1~ppa1~maverick 0
100 /var/lib/dpkg/status

What does this mean? What will it do?
posted by jozxyqk at 9:25 AM on April 25, 2012

Response by poster: Huh.. upon further investigation.. maybe xbmc specifically was _always_ installed only from a PPA? It's been a long time.

But the question still applies more generally, to other packages that might be "newer on PPA" but exist in the main repos.
posted by jozxyqk at 10:01 AM on April 25, 2012

The presence of archive lines as sources doesn't matter. PPAs may be disabled during "update-manager" upgrades. Repeat after me: Packages are never downgraded.

Now, what does the two "apt-cache policy ..." results mean? With the PPA, you have out there in the world a source to download that package and you already have it installed locally. Without the PPA, you have only it installed already (and no place to download it from).

If the "Installed" version and "candidate" version are the same, then there's no change when you upgrade.
posted by cmiller at 10:10 AM on April 25, 2012

Best answer: If you want to check what will happen for a particular version on new distro, change the APT sources.list file to say "precise" instead of "maverick" and then "apt-cache policy ...".
posted by cmiller at 10:18 AM on April 25, 2012

Response by poster: Followup for those who care.. I finally did the upgrade to 11.04 and it went really smoothly with no major problems. So I guess I had nothing to worry about.
I will let it run on 11.04 for a little while before taking the next upgrade step; at least I know I'm going to be getting security updates in the meantime.
posted by jozxyqk at 2:12 PM on May 4, 2012