Ugh. Found the cause. The ubuntu-desktop package depends on lightdm but it doesn't depend on any greeter. So upgrading will pull in lightdm, replace GDM but have no greeter installed. What is supposed to happen then is failsafe X starts and prompts you to fix the error, but that doesn't work either.
Solution is to make ubuntu-desktop depend on unity-greeter. ** Changed in: lightdm (Ubuntu) Status: Incomplete => Triaged ** Also affects: ubuntu-meta (Ubuntu) Importance: Undecided Status: New ** Changed in: ubuntu-meta (Ubuntu) Status: New => Triaged ** Changed in: ubuntu-meta (Ubuntu) Importance: Undecided => High ** Summary changed: - After latest upgrade of oneiric, Lightdm (lightdm) or Xserver not working + ubuntu-desktop package depends on lightdm but no greeter -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/804171 Title: ubuntu-desktop package depends on lightdm but no greeter To manage notifications about this bug go to: https://bugs.launchpad.net/hundredpapercuts/+bug/804171/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs