Black screen on Kubuntu 22 LXD container

[Duncan]

Michael Eager posted on Wed, 10 Aug 2022 06:40:46 -0700 as excerpted:

> I'm running Kubuntu 22.04 in an LXD container.
> 
> When I connect using x2go, KDE starts up (I see the splash screen) but
> then the screen goes black with a cursor. After a short time, the lock
> screen is shown, with password field, so I think that x2go is working.
> When I log in, the screen goes black.  There is a cursor, but neither
> left nor right clicks have any effect.
> 
> Something similar happens running tightvnc-server:  I can open a remote
> window using vncviewer but it is all gray and unresponsive.
> 
> In both x2go and vnc windows, I can bring up a terminal window using
> alt-F2 to display krunner and then running konsole. When I look at
> environment symbols, I see the following:
> 
> XDG_SESSION_TYPE=tty XDG_CURRENT_DESKTOP=KDE
> 
> SDDM appears to be running, as does plasma_session.
> 
> Anyone have any suggestions?

So my environment is /way/ different than yours (on the physical machine 
not a container and I start plasma from a CLI login, no graphical login 
manager) and I don't have any direct fix-it help to offer, but here's 
hoping this is at least of some help...

Since you can bring up krunner and run konsole (and presumably whatever 
other apps) from there...

The problem is that while most of the plasma environment is evidently 
running, plasmashell (which provides the desktop, panels, etc) is crashing 
or unresponsive, leaving nothing to paint a background or provide the 
usual shell.

Use your favorite task manager utility to check if it's running, either 
idle or busy-looping.  I like/use htop in a konsole window, but regular 
top should work, or an appropriate ps invocation (if you're like me you'd 
have to man ps to get an appropriate commandline, top/htop are nicer in 
that regard), or pgrep plasmashell, or... if you're lucky a ctrl-esc will 
launch plasma's own system activity task-lister or you can launch your 
favorite graphical alternative from konsole/krunner.

If it's running, kill it (htop and plasma's system activity lister can do 
it from within the app, or use kill/killall/pkill/whatever).

Then try starting plasmashell manually.  If you're lucky the restart will 
get it all going and you'll be fine from there.  If not, try restarting 
from konsole and see if it outputs any useful debugging as it crashes.  
OTOH, kde apps are /infamous/ for spitting out so much actually harmless 
effectively developer-interest-only "noise" that it can be impossible for 
an ordinary user like you or I to tell if there's anything actually of use 
in all that noise or not, especially if you don't have the output from a 
normal run to compare it against, so YMMV, but it's worth a shot.

Meanwhile, just saying kubuntu 22.04 doesn't really tell non-(k)ubuntu-
users what plasma and frameworks versions you're running.  Since you can 
run konsole, do so, then from its menu select help, about konsole.  There, 
you can get the version information (on live-git-master plasma/frameworks 
updated a few days ago I see version 22.11.70, that's the konsole/plasma 
version) to report, and then on the components tab, the frameworks and qt 
versions (5.97.0 and 5.15.5 respectively, here), along with the windowing 
system (probably x11 for you, it's wayland here).  If you can find it 
other info like the vnc/x2go versions, LXD version info whatever form it 
takes (I wouldn't know), etc, might be useful as well.  Posting that 
should increase the chances of someone else being able to see they are 
running something comparable and thus being able to help even if not on 
(k)ubuntu, tho of course there's no guarantee.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman