I've made a long search thru all posts in the forum, and no one could help resolving my problem:
The machine is a desktop with only linux and an nvidia GeForce GT 430.
After the upgrade from kubuntu 14.10 to kubuntu 15.04, the new sddm login appear, then, after the login and the first loading bar, a blank black screen with only the active cursor appear, and only the alt
+F2
works, even if the little window in the upper side doesn't execute any command.
The same upgrade in my notebook (with a dual linux-win and an nvidia Quadro 4000M) work just fine.
I've tried to purge and reinstall every version of the nvidia driver, I've tried to write the specifics of the monitor in the xorg.conf created by nvidia-xconfig, I've even purged and reinstalled the plasma-desktop, first the 5.2 then the 5.3 .
Nothing. No errors on dmesg, no errors on Xorg.0.log .
Now, can someone please suggest something that I can try? I would be really grateful. Thanks.
UPDATE:
as suggested by Zacharee1, I've installed the gdm and gnome-desktop packages and it works, so the problem is in the plasma-desktop. I've reinstalled sddm and plasma-desktop, but nothing has changed regarding sddm.
But now, if logged in in textual mode, with startx the graphic session works.
Best Answer
I think I have narrowed this down a bit. By first removing my fglrx proprietary AMD graphics driver, so that Ctl-Alt-F1 would get me a useful terminal, and then by moving the following file aside, I could get from the black screen back to a reasonably healthy desktop:
Testing could proceed rapidly, because, after each of many tests moving aside various $HOME/.config and $HOME/.cache files, I could quickly see if that got me a black screen, or a reasonable sddm desktop, by invoking the command:
On the occasions where I got a black screen, I saw signs of a segfault crash in the following log files for kactivitymanage:
A typical kern.log or syslog entry was:
A typical apport.log entry was:
Examining my customized (and failing) .config/plasma-org.kde.plasma.desktop-appletsrc, I can see further evidence of the problem. The bad (black) plasma config file is missing the following stuff (no wonder the screen is black - almost nothing is configured ):
So ... it would appear that something is writing out a bad plasma config file, with much of the good stuff removed.