Here's the situation: I have a separate /home partition to make installs and upgrades easy. I just installed the latest version of Ubuntu 14.04. Everything was great. I installed the LXDE desktop (not Lubuntu) via synaptic. Everything works fine. I could boot into the Unity desktop and the LXDE desktop.

Then I installed KDE desktop via synaptic. The boot splash changed, which is fine, but now I can only boot into KDE or LDXE. If I try to boot into Unity, I'm stuck at the splash screen. If I push the power button, the splash goes away, and I see the tail end of a shut-down, as if I'd executed sudo shutdown -h now in a terminal.

I could simply reinstall, and never use KDE, but I like that option from time to time.


I found the problem. KDE switched the default display manager to KDM which didn't want to play with Unity. All I needed to do was switch back to lightdm using

 sudo dpkg-reconfigure lightdm

as suggested in this question/answer.

  • 5
    You should post that as an answer to your own question. Or I can do it for you :D – Kaz Wolfe Aug 30 '14 at 21:49
  • 3
    @Marc Especially, if you're interested in other workarounds/solutions (besides the one you found)--such as a way to let Unity work while still using KDM as the display manager--then I'd suggest editing your question to add information about which packages you installed in Synaptic to get KDE. – Eliah Kagan Aug 31 '14 at 3:20
  • did you purged unity ? – A Umar Mukthar Sep 6 '14 at 2:36
  • Have a look askubuntu.com/questions/491044/…. – A Umar Mukthar Sep 6 '14 at 3:11
  • What is the outcome of ls -l /usr/share/xsessions/ in terminal. – A Umar Mukthar Sep 6 '14 at 7:40

In accordance to the edit to your question and my comment, I felt like I should upload this answer...

It sounds like your display managers are not configured properly. You can reconfigure LightDM (the default one) by running:

sudo dpkg-reconfigure lightdm

You will be prompted to select a default DM. In this case, select LightDM.

Reboot (or restart X) and your problem will be solved!

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