I have a new System76 Lemur Laptop. It worked fine for a week. I installed Kubuntu, it worked fine. Then I upgraded to Kubuntu 16.04 LTS and the system doesn't boot fully anymore. The Kubuntu logo flashes but then never displays the login UI, I just see black. I can get a TTY by pressing CTRL+ALT+F1 key. I can run startx -- :1 from the TTY to get a bare bones graphical interface.

How can I get a usable graphical interface?

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    It didn't work after the first long tty, then I rebooted holding down shift and chose the latest os recovery; fixed broken pkgs and rebooted. It worked! – user559625 Jun 21 '16 at 14:00
  • Same here. I start to hate K/Ubuntu! After every update/upgrade something essential is broken and the user is left with a blinking cursor... These are the moments when I regret to have switched to free and open (but crappy and broken) software :( – Sliq Dec 1 '16 at 20:16
sudo dpkg-reconfigure sddm

and selecting sddm worked for me.

  • Worked for me. I guess @Enkouyami's answer is a bit more hard-core approach, if above fails. – Aleksandar Pavić Mar 2 '17 at 20:47
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    Take care: in my case this messed up my whole system! Needed to start the rescue console ... -1 – Trinimon May 23 '17 at 18:15


sudo apt-get install --reinstall kubuntu-desktop plasma-desktop plasma-desktop-data sddm xorg xserver-xorg-core xserver-xorg-video-intel && sudo dpkg-reconfigure sddm

The 1st part will reinstall kubuntu's KDE plasma, the X11 display server, the sddm display manager, and the intel video driver; the next will allow you to set it as the default display manager. If some of those packages aren't installed, it will attempt to install them.

Logs are located at /var/log. Look for the log for Xorg and sddm.

  • Ok @DavidFoerster, I have clarified my position. – Enkouyami Apr 23 '16 at 22:30
  • Thanks, but this didn't work. I still see the same problems. Is there some debug log that I should look at that might offer some clues? – rrenaud Apr 25 '16 at 2:10
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    @rrenaud Run sudo apt-get install --reinstall sddm; sudo dpkg-reconfigure sddm to reinstall & configure the sddm display manager. Logs are located at /var/log/ and look for the ones for sddm and Xorg. – Enkouyami Apr 25 '16 at 3:44
  • Also, could you make a bug report using ubuntu-bug xorg? You will probably get a lot more help than you could from askubuntu. – Enkouyami May 1 '16 at 22:42
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    Reconfigure of sddm without reinstall worked for me. – musiKk Jul 1 '16 at 10:11

Note - This message only aims at proprietary nvidia drivers users. I'm not sure if your laptops has one, but it may help for other people that were in the same situation. :

I just encountered a similar issue after updating my Kubuntu 16.04 setup (it already worked fine with it). Messing around KDE packages didn't help. However I noticed that Plasma was actually working but I didn't get any real visual feedback (right click worked as if plasma was properly started). I could start in a konsole using alt+f2 and blindly launching it. Manually restarting KWin (kwin_x11 --replace) showed me that compositing got disabled because of the lack of GLX extension in the X server. It was confirmed by glxgears not willing to start.

So I dropped in a TTY, logged in, sudo service lightdm stop (note : the default DM under Kubuntu is sddm so it most likely would be sudo service sddm stop), reinstalled the nvidia drivers, rebooted and it was back working.

I wonder if it was just about the X.org config (so try messing around nvidia-xconfig first) that got replaced or if the upgrade nuked up some GLX libraries.

Hopefully this will help you and some others going by!

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    The system76 lemur laptops use Intel integrated graphics. – Enkouyami May 1 '16 at 22:36

Same problem. I held the shift key down during boot and got to a menu where I chose "advanced options," then selected "upstart." At least I can do my office work now. Unknown how to make systemd, the new type of booting up, function.

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