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?
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
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.
don't trust KDE plasma desktop, after you're happy with your widget setup backup the config
mv ~/.config/plasma-org.kde.plasma.desktop-appletsrc ~/.config/plasma-org.kde.plasma.desktop-appletsrc.bak
now to fix your problem delete the corrupted config
rm ~/.config/plasma-org.kde.plasma.desktop-appletsrc
then restart the kde
qdbus org.kde.ksmserver /KSMServer logout 0 0 0
whenever this happens replace your config with the current one this happens a lot to me sometimes when I connect dual monitor
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
You can reinstall the plasma-desktop to use KDE again:
sudo apt-get reinstall plasma-desktop
Alternatively you can use the dpkg-reconfigure to reconfig your plasma desktop:
sudo dpkg-reconfigure plasma-desktop
This is a problem for some kde updates.
http://bugs.launchpad.net/ubuntu/+source/kdeadmin/+bug/331192/
I also do the backup of ~/.config/plasma-org.kde.plasma.desktop-appletsrc to restore on the odd occasion things really break but sometimes all you need is to get back a missing panel (including taskbars) or widget by doing the following:
It's quicker and less hassle as it doesn't require you to kill programs/log out & in.
To reload the Plasma desktop if something got hung up somehow in the current session:
plasmashell --replace &
To re-add the default panel if it permanently got lost, i.e. if even reloading Plasma or logging out and in again doesn't help:
Right-click on desktop -> Add Panel -> Default Panel.
It helped me to right-click desktop, "Add Panel" -> "Default Panel". I got my panel back exactly the way I've configured it before.
I have a dual display setup:
I face 2 issues:
Resolution for issue #2:
I run below commands configured as keyboard shortcut.
Turn ON TV and turn OFF Monitor
xrasengan -on HDMI-0 -off DP-2
Turn ON Monitor and turn OFF TV
xrasengan --force -on DP-2 -off HDMI-0
Inspired by Fathy's answer and this OP on the KDE forum, I opened the file
~/.config/plasma-org.kde.plasma.desktop-appletsrc
and replaced every occurrence of the line
lastScreen=n
for some number n with
lastScreen=0.
I then "restarted the kde":
qdbus org.kde.ksmserver /KSMServer logout 0 0 0
and all my lost plasmashell panels (containing things such as the global menu bar, the launcher, the taskbar, the system tray) reappeared, including ones that I had long lost to non-existent screens, had given up on and forgotten about.
