I tried to reproduce the problem using a Xubuntu 14.04 image and everything worked as expected:
http://people.canonical.com/~amilone/xubuntu-output.log The main problem is that systems older than 14.04 might still have a /etc/lightdm/lightdm.conf that was altered by older nvidia-prime releases. I thought lightdm would take care of the issue by removing such configuration file but I was wrong. This is the preinst script from lightdm in trusty: if dpkg-maintscript-helper supports mv_conffile; then dpkg-maintscript-helper mv_conffile \ /etc/lightdm.conf \ /etc/lightdm/lightdm.conf \ 0.3.7-0ubuntu2 -- "$@" fi I believe 0.3.7-0ubuntu2 should be updated to a more recent release such as 1.10.1-0ubuntu1~. This is something that we should deal with in the lightdm package though. I don't think it would be right for nvidia-prime to remove lightdm's configuration files. ** Also affects: lightdm (Ubuntu) Importance: Undecided Status: New ** Changed in: lightdm (Ubuntu) Status: New => Triaged ** Changed in: lightdm (Ubuntu) Importance: Undecided => High -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1267442 Title: Install nvidia-331 on X/K/Lubuntu results in unbootable machine To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/lightdm/+bug/1267442/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs