After upgrade 12.04 -> 14.04 there was no display manager (kdm or lightdm)

Additional info: The KDE packages of the 12.04 system were from the kubuntu-backports-ppa.

kubuntu-desktop was not installed.

Well, random guess of the day: lightdm was not installed during the upgrade because kubuntu-desktop was not present (thus no dependency tie to lightm) and kdm was removed in the post-upgrade cleanup either because there were no dependency chains to in anymore or there is special magic that marked kdm for removal (probably latter I am guessing).

Other random comment: I was under the impression that update-manager will try to figure out which desktop package to force into the installation in case none is installed, so technically this should not have happend... however there is no indication of any such business in the logs... this probably needs to be reproduced in an equal environment.

Indeed I don't have kubuntu-desktop installed because I removed one (or more) of it's dependencies a long time ago. I think this is not uncommon, though. At the end of the upgrade I didn't let upgrade-manager clean up unused packages, therefore the reason for the removal of kdm seems to be something else.

For this upgrade test I made a copy of my main system to an extra partition and therefore I can try the upgrade again to verify if a possible fix works.

Oh, that is handy xD

Just to be sure though, you did not get any query asking you whether *-desktop should be installed?

No, there was no such question.

From the logs we can see the following:

2013-12-29 11:16:30,144 DEBUG need_server_mode(): can not find a desktop meta package or key deps, running in server mode
2013-12-29 11:16:30,144 DEBUG checkViewDepends()

Looking at the ubuntu-release-upgrader code we see the following:

        for key in metapkgs:
            # if it is installed we are done
            if key in self and self[key].is_installed:
                logging.debug("need_server_mode(): run in 'desktop' mode, (because of pkg '%s')" % key)
                return False
            # if it is not installed, but its key depends are installed
            # we are done too (we auto-select the package later)
            deps_found = True
            for pkg in self.config.getlist(key, "KeyDependencies"):
                deps_found &= pkg in self and self[pkg].is_installed

KeyDependencies for kubuntu-desktop are:

[kubuntu-desktop]
KeyDependencies=kdm, kubuntu-artwork

Are there some other packages that should be added?

Obviously the keydependencies have not been found even though kdm was installed. Or is it required to find both (all) keydependencies? Then the explanation would be that kubuntu-artwork seems not to be available from the kubuntu-backports-ppa and therefore wasn't installed.

Would it help if I send a list of the installed packages from before the upgrade?

I made some more experiments. I used the default installation of Kubuntu 12.04 and then upgraded to the kubuntu-backports-ppa. Then I upgraded to 14.04 and the result was that lightdm was installed, no matter if kubuntu-desktop was installed or not.

Then I removed the other packages which were not installed on the system which produced the bug in question. The result of the upgrade to 14.04 was that kdm was removed and lightdm was not installed. I had a closer look at the packages and found that ubuntu-minimal and ubuntu-standard were not installed, so I repeated the experiment with these packages included, but the result stayed the same (no display manager).

While you had kdm installed it was installed from a ppa.

kdm 4:4.11.3-0ubuntu0.1~ubuntu12.04~ppa1 0

I'd image this figures into the calculation.

Two things:

1. if both are required then that has been broken for a long time because there has not been a kubuntu-artwork package for at least 5 years
2. if PPAness does affect the calculation, then I guess that needs to change to some degree since we pretty much support our own PPAs :S

Assuming 1. doesn't apply, enhancing the keydeps with some actual kubuntu stuff would help sufficiently though:
kubuntu-settings-desktop, kubuntu-notification-helper, kubuntu-debug-installer, kubuntu-web-shortcuts

Those do not get updates via PPAs and at the end of the day I suppose those are the most reliable indicators of a kubuntu installation.

Fix committed to bzr. Using:
- plasma-desktop & kubuntu-settings-desktop
- plasma-netbook & kubuntu-settings-netbook

This bug was fixed in the package ubuntu-release-upgrader - 1:0.210

---------------
ubuntu-release-upgrader (1:0.210) trusty; urgency=low

  [ Brian Murray ]
  * data/DistUpgrade.cfg.precise: change kernel removals to 3.2.0
  * source_ubuntu-release-upgrader.py: collect dmesg info when reporting
    upgrade failures
  * Utilize new downloaded event from update-manager thereby speeding up usage
    of MetaReleaseCore. Thanks to Anders Kaseorg for the patch.
  * Don't build depend on scrollkeeper thanks to Jeremy Bicha for the patch.

  [ Harald Sitter ]
  * data/DistUpgrade.cfg.precise: change kubuntu-desktop key dependencies to
    plasma-desktop, kubuntu-default-settings (previous ones did not exist or
    were simply bad key dependencies) LP: #1264887
    + Same for kubuntu-netbook using plasma-netbook,
       kubuntu-netbook-default-settings.
  * data/DistUpgrade.cfg: change kubuntu-desktop key dependencies to
    plasma-desktop, kubuntu-settings-desktop
    + Same for kubuntu-netbook using plasma-netbook, kubuntu-settings-netbook
 -- Brian Murray <email address hidden> Thu, 23 Jan 2014 16:14:37 -0800

Today I repeated the upgrade on the test-partition and I can confirm that the bug is fixed. Thanks for taking care of the issue.