sudo add-apt-repository ppa:kubuntu-ppa/backports 
sudo apt-get update 
sudo apt-get upgrade

and restarting the computer, I got many problems on KDE (certainly related to the upgrade, maybe related to the kubuntu-ppa/backports):

  • Alt+F4 doesn't close windows
  • Alt+Tab doesn't switch between windows
  • windows' borders, title bar & buttons are not visible
  • opened applications don't appear on the Task Manager
  • Panel doesn't unhide if a window is maximized
  • F2 (rename object) doesn't work in Dolphin

Would you have any idea about how to solve it or, at least, the name of the component that is faulty so I can focus my web searches on it?


2 Answers 2


Read man apt-get

Looks like you simply forgot to run:

sudo apt-get dist-upgrade as the third command to follow the two others on the command-line. This it is essential to resolve dependencies and install missing packages that were removed before.

But it's o.k. if it could resolve it the investigating way. Don't forget to mark your question as solved.

  • thank you! This answer is probably better than mine. However, since I cannot reproduce the error to test it, I marked mine as the accepted answer, and put a comment referencing to yours.
    – toliveira
    Commented Dec 23, 2015 at 11:35

[Looking for "kde no title bar" guided me to the solution.]

kde-window-manager was removed during the upgrade, reinstalling it fixed the problem.

sudo apt-get install kde-window-manager
  • Try @ellisistfroh suggestion before using this one.
    – toliveira
    Commented Dec 23, 2015 at 11:32

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