KDE taskbar missing
I'm not sure what I pressed or clicked but I can no longer see the taskbar in KDE. I'm not finding any desktop switching keys though ALT+Tab still switches to already opened windows. Right-clicking on the blank empty black background does nothing. On Windows 7 I'd just CTRL+ALT+Delete, kill explorer.exe and start explorer again.
How do I show the missing taskbar in KDE?
Solution 1:
Killing the plasmashell process and restarting it from a terminal helped me in this situation.
To terminate the plasmashell process you will need access to a terminal. On most distributions you can get a terminal with CTRL+ALT+F1 or CTRL+ALT+F2. Don't worry, your screen will turn black and you will be prompted to log in with your username and password.
To get back to your regular KDE session you will need to press CTRL+ALT+F7 or CTRL+ALT+F1!
Once you have opened a terminal session you can stop the plasmashell process with
killall plasmashell
and start it again with
plasmashell &
The & is only required if you want to be able to close the terminal or want to be able to keep using it for other commands. It will start the plasmashell process in the background so it does not close with the terminal and does not keep blocking the terminal from receiving further input.
Alternatively you can kill the plasmashell process in your terminal and then immediately return to KDE and hit your hotkey for krunner, which is afaik ALT+F2 by default, and enter plasmashell there.
Solution 2:
In my case the ~/.config/plasma-org.kde.plasma.desktop-appletsrc file got in a bad state (from switching from laptop to external monitor).
Rather than trying to fix the file, I just deleted it (ALT-F2 "konsole"):
rm ~/.config/plasma-org.kde.plasma.desktop-appletsrc
Then logout from the session (ALT-F2 "logout") Log back in, and the taskbar is now visible, some settings were lost (background color, ...)
I now personally keep a backup of the file, in case it happens again:
cp ~/.config/plasma-org.kde.plasma.desktop-appletsrc ~/.config/plasma-org.kde.plasma.desktop-appletsrc.backup
Solution 3:
As I faced exactly the same issue on my notebook with Intel+Nvidia Optimus (proprietary driver), my solution is to add
xrandr --output VGA-0 --off
to /usr/share/sddm/scripts/Xsetup
Though removing ~/.config files is a default reaction, it didn't solve my problem. Anyway I'd recommend renaming configuration files if needed for testing purposes:
mv ~/.config/plasma-org.kde.plasma.desktop-appletsrc ~/.config/plasma-org.kde.plasma.desktop-appletsrc.bkp
It is a known bug that nvidia drivers add CTR device VGA-0 even if it is not connected. So this caused plasmashell to crash at login time. A quite comprehensible reaction to such a noobish bug IMHO.
I also tried to disable VGA-0 in KDE Display Settings, but these settings come into effect after login. Xsetup is run before sddm starts, so the CTR device is disabled even before startplasmashell-X11 which is executed by /usr/share/xsessions/plasma.desktop
Hope this helps to solve it without plasmashell --replace & because that command slows down login time, plus grinded my nerves.
Cheers