I realise that there are similar questions on this problem for Ubuntu, including a question that I asked myself, but I have the same problem with Kubuntu 15.04.

My Kubuntu system is set to a resolution of 1920 x 1080 through Display Configuration settings. On system start-up (or after logging out and logging in again), the 1920 x 1080 resolution is not applied and the login screen resolution is incorrectly set to the native screen resolution of 3840 x 2160, but changes back to the correct setting after logging in.

I was interested in why this seems to be occurring, and if there are any solutions that will apply the correct settings on system start-up and after log in. For reference, my laptop is a Lenovo Y50 UHD.

  • I really would LOVE the reputation points, but I don't think it would be right for me to take credit for someone else's ideas, unless of course I had improved upon them. I think this question has been asked and answered....askubuntu.com/questions/73804/wrong-login-screen-resolution – user175999 May 30 '15 at 5:48
  • I referenced it in the question I asked before but I don't think they apply to Kubuntu (and there were also some other problems that I mentioned in that post). Does Kubuntu use LightDM as the display manager? – amy May 30 '15 at 9:08

The way I solved this on my laptop:

  1. Create a new xorg.conf file and copy it to /etc/X11

  2. Under Section "Monitor" add the following line

    Option "PreferredMode" "1920x1080"
  3. Under Section "Screen" in SubSection "Display" add the Modes entry below the Depth line as shown.

    Viewport   0 0
    Depth     24
    Modes "1920x1080"

These changes will make "1920x1080" the default resolution for login and session.

To generate the xorg.conf file you need to go to tty1 (Ctrl +ALT+F1) and after login stop the X server (sudo service lightdm stop) and issue sudo X -configure. Then copy the temporary xorg.conf.new file to /etc/X11/xorg.conf and reboot.


Kubuntu 15.04 doesn't have lightm for the login screen, instead the new sddm. It is still in the development phase actually. Look for issues here.


I had the same issue and found there were to patch this but without a real reason.

According to documentation of sddm:

Path of script to execute when starting the display server. Default value is "/usr/share/sddm/scripts/Xsetup".

The obvious solution is therefore to add the xrandr command to /usr/share/sddm/scripts/Xsetup. This can be easily retrieve with ARandR.

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