I'm fairly new to Linux in general, so bear with me!

On a fresh install of Plasma 5.2 on Kubuntu 14.10, I'm getting a black screen on login.

• The login screen is unaffected.
• Once logged in: I can still move the mouse, but the entire screen is black with the exception of the panel (which is blank).
• Before this started, plasmashell would crash randomly.
• Trying to restart plasmashell via console (Ctrl+Alt+F1-6) returns "qxcbConnection could not connect to display"
• Using "export DISPLAY=0:" causes it to return "qxcbConnection could not connect to display 0:"
• Trying to run other programs via console gives a similar result
• Programs that were running before the issue started still launch when I log back in.
• KSysGuard (one of said programs) shows plasmashell running on login, but it stops when I mouse over the panel.
• Resetting my /home directory fixes the issue, but it comes back after a few days
• Reinstalling Kubuntu (excluding /home partition) doesn't fix it
• Logging in as another user works fine
• Uninstalling Nvidia drivers and using open-source ones doesn't fix it

I would assume this has something to do with a config setting somewhere, but I can't figure out what specifically is causing the problem. This has happened each time I've reinstalled. The first time took a week, and the second only a day or two. I can't think of anything specific that I was doing at the time except for maybe playing with ALSA?

I'm out of ideas. Any help would be appreciated!

couple things to try to isolate the problem

1) rename your Kwin config then restart kwin with

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mv ~/.config/kwinrc ~/.config/kwinrc-old && kwin_x11 --replace

2) move your plasma files then restart Plasma forcing a return to the defaults

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kquitapp plasmashell
 sleep 20s
 mkdir -p $HOME/plasma-config/
 mv ~/.config/plasma* $HOME/plasma-config/
plasmashell &


This should tell if its a Kwin or a Plasma config issue

note: this is the std code we used for KDE 4 which I've adjusted (hopefully correctly) for Plasma 5

mv ~/.config/kwinrc ~/.config/kwinrc-old && kwin_x11 --replace

Returned "FATAL ERROR while trying to open display". The /kwinrc moved, but nothing changed after a reboot.

kquitapp plasmashell
sleep 20s
mkdir -p $HOME/plasma-config/
mv ~/.config/plasma* $HOME/plasma-config/
plasmashell &

"Application plasmashell could not be found using service org.kde.plasmashell and path /MainApplication." This also made my desktop freak out, if that tells you anything. Should I kill the process some other way?

google01103 wrote:This should tell if its a Kwin or a Plasma config issue

"Programs that were running before the issue started still launch when I log back in."
"KSysGuard (one of said programs) shows plasmashell running on login, but it stops when I mouse over the panel."

@Physicist:
"export DISPLAY=0:"
try

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export DISPLAY=:0

Don't you get a DrKonqui window with a "developer information" tab for the plasmashell crash? (ie. a backtrace)

Don't you get a DrKonqui window with a "developer information" tab for the plasmashell crash? (ie. a backtrace)

Before the PerpetualBlackScreenOfDoom™ I would get one after a crash, but I kind of brushed it off a common issue that I would worry about later. It doesn't show up now.

EDIT:

try "export DISPLAY=:0"

I tried this and ran plasmashell, and a wall of text was spat out. When I switched back to my desktop, it was on the fritz again. I could, however, barely make out a DrKonqui prompt indicating that plasmashell had crashed.

DrKonqui is a dialog, not a prompt.
If you don't get it (despite a certain plasmashell crash) that's gonna be tricky, because you'll have to gdb plasmashell to get a backtrace.

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gdb --args plasmashell --nofork 2>&1 | tee plasmashell.dbg

this will copy the gdb output into plasmashell.dbg
On gdb prompt, issue "run", wait for the crash, then issue "bt" and press enter until the last line of the backtrace is reached.
The issue "detach" and "quit".

Sorry for the slow response. Here's the output, including the backtrace:

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Reading symbols from plasmashell...(no debugging symbols found)...done.
(gdb) run
Starting program: /usr/bin/plasmashell --nofork
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
QXcbConnection: Could not connect to display

Program received signal SIGABRT, Aborted.
0x00007ffff2b87e37 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
56   ../nptl/sysdeps/unix/sysv/linux/raise.c: No such file or directory.
(gdb) bt
#0  0x00007ffff2b87e37 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
#1  0x00007ffff2b89528 in __GI_abort () at abort.c:89
#2  0x00007ffff32b64df in QMessageLogger::fatal(char const*, ...) const () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#3  0x00007fffe4da2cf1 in ?? () from /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqxcb.so
#4  0x00007fffe4da63fe in ?? () from /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqxcb.so
#5  0x00007fffe4dba00b in ?? () from /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqxcb.so
#6  0x00007ffff3838e62 in QPlatformIntegrationFactory::create(QString const&, QStringList const&, int&, char**, QString const&) () from /usr/lib/x86_64-linux-gnu/libQt5Gui.so.5
#7  0x00007ffff3844896 in QGuiApplicationPrivate::createPlatformIntegration() () from /usr/lib/x86_64-linux-gnu/libQt5Gui.so.5
#8  0x00007ffff384561d in QGuiApplicationPrivate::createEventDispatcher() () from /usr/lib/x86_64-linux-gnu/libQt5Gui.so.5
#9  0x00007ffff3505fbf in QCoreApplication::init() () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#10 0x00007ffff3506026 in QCoreApplication::QCoreApplication(QCoreApplicationPrivate&) () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#11 0x00007ffff3847769 in QGuiApplication::QGuiApplication(QGuiApplicationPrivate&) () from /usr/lib/x86_64-linux-gnu/libQt5Gui.so.5
#12 0x00007ffff3e0344d in QApplication::QApplication(int&, char**, int) () from /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#13 0x000000000042f310 in main ()


I've tried removing everything related to Plasma and Kwin in ~/.config, but the issue persists. Removing ~/.cache does bring everything back to normal, but I still don't know the source of the problem.

Hi!

I have just installed the vivid iso with plasma 5 and I'm experiencing some problems with black screen too. I'm not a deep linux user, but I can handle the basics. Is there any way I could fix this the black screen problem? Mouse pointer shows up an Alt+Space works too, but I can't open any application. I've tried recovery mode and dpkg to fix packages, but didn't work.

In case there's no simple solution, is there a "correct way" to reinstall the distro? I'm using it along with ubuntu 14.04 and windows 8.1. The other OS are working just fine.

Thanks!

> QXcbConnection: Could not connect to display
This btw. means that you forgot to "export DISPLAY=:0"

> Removing ~/.cache does bring everything back
Corrupt cache (plasmashell related) - there're bugreports in this regard related to a (previously) full HDD

I installed kubuntu 15.04 yesterday while i am happy with all the features and UI, but I am facing the above issue since the install.

It goes away after renaming the .cache folder and forcing to defaults, but after some time it comes back.

Since install i am not able to run the system for not more than 3 hrs at a stretch plasmashell crashes randomly and then reboot brings us to black screen.
I hope this gets solved soon

I am willing to provide more details if somebody tells me how to get them (e.g. backtrace or any other information which will help the developers solve this)

thank you

Depending on the actual versions, this might have been resolved:
https://codereview.qt-project.org/#/c/110346/
https://git.reviewboard.kde.org/r/122549/#review76212

Same problem for me. Resolved by deleting the ~/.cache folder

Same thing here Running Kubuntu 15.04 on AMD64.
Though deleting .cache restores session, default panel has to be manually re-added.
Apparently has to do with the plasma .lock

Related: https://bugs.kde.org/show_bug.cgi?id=344032

Hey all,

Same issue here.
I see the bug listing ... but how do we actually fix this issue, please?