Problem
Multiple users have reported that Fedora 43 KDE sometimes boots to a black screen, instead of a login screen (SDDM).
Cause
There seem to be multiple different problems causing this behavior:
- When certain external monitors are connected to a laptop (mostly with Nvidia GPUs, it seems), the login screen fails to start.
- There seems to be a race condition when performing a handoff from ‘plymouth’ (the component that displays a graphical boot process) to ‘sddm’ (the login manager used on KDE). Most people seem to be running AMD iGPUs, but we have some reports with other GPUs as well.
Related Issues
Bugzilla report (plymouth handoff): #2404966
KDE bug report (external monitor): https://bugs.kde.org/show_bug.cgi?id=511490
Solutions and workarounds
Both issues should be fixed as of kwin 6.5.2, which has been the stable version for some time now. So the issues should be resolved on installed systems that are up to date. If you previously applied a workaround, you can try reversing it - to reverse the “remove rhgb” workaround and get pretty graphical boot back, run sudo grubby --update-kernel=ALL --args=rhgb. Or you can leave things as they are if you don’t mind the non-graphical boot.
Live images respins
If you are affected by either issue when trying to boot the official KDE live image, you can try to use new respins (rebuilds) of Fedora 43 Live images. They contain updated packages and therefore these issues should be resolved on them. Please note, however, that they are unofficial and are not validated by the Quality team - they might contain new problems instead. You can find Live respins here:
https://dl.fedoraproject.org/pub/alt/live-respins/
External monitor issue workaround
Simply disconnect the external monitor before booting.
Plymouth handoff workaround
Several users have reported that disabling the graphical boot process avoids the problem. This will give you a somewhat uglier text boot process. It doesn’t have any other consequence.
You can do this permanently by running sudo grubby --update-kernel=ALL --remove-args=rhgb. To reverse this once the bug is fixed, you can do sudo grubby --update-kernel=ALL --args=rhgb.
If you want to test the change temporarily first, or you can’t manage to boot far enough to run that command, you can edit the arguments at boot time from the Fedora boot menu. If the Fedora boot menu does not appear on your screen, try pressing Esc or F8 repeatedly while the system is booting. On the Fedora boot menu, hit e to edit the default boot entry, go down to the line that starts linux, press End to go to the very end of the line (or use arrow keys). It will likely end rhgb quiet. You want to go back through the word quiet and delete the word rhgb. Then hit Ctrl-x to proceed with boot.