pkgProblemResolver logs cryptic, unactionable errors

[Lupius]

I've been having trouble upgrading Ubuntu 13.10 to 14.04 due to broken dependencies reported by pkgProblemResolver. Researched all over the internet for a definitive solution and could not find any. The most commonly offered solutions are of drastic measures such as removing 3rd party PPAs, blindly remove *possible* offending packages, manually changing Ubuntu PPAs to the newer release channel, or even a clean install from an ISO.

I could not for the life of me find any documentation that actually explains what is being logged by pkgProblemResolver. For example take the following block:

Broken libclutter-1.0-0:amd64 Breaks on libcogl12 [ amd64 ] < 1.14.0-2 > ( libs )
  Considering libcogl12:amd64 55 as a solution to libclutter-1.0-0:amd64 52
  MarkKeep libclutter-1.0-0 [ amd64 ] < 1.14.4-3 -> 1.16.4-0ubuntu2 > ( libs ) FU=0
  Holding Back libclutter-1.0-0:amd64 rather than change libcogl12:amd64

I'm a senior software engineer with 4+ years experience of using Ubuntu as a dev environement, and this error log is complete gibberish to me. I want to understand exactly how the dependency is broken in the first place and how the resolution logic arrived at MarkKeep, so that I can have a systematic approach for addressing these errors without resorting to any of the earlier mentioned drastic measures.

[Brian Murray (brian-murray)]

You might find the following blog post helpful:

http://www.chiark.greenend.org.uk/ucgi/~cjwatson/blosxom/ubuntu/2012-01-29-apt-resolver-bugs.html