Login failed on sddm screen: fix or workaround sought

English Install/Boot/Login
1

I am encountering occasional “Login failed” refusals-to-login from the KDE Plasma (5.27.9) SDDM screen. These have occurred after power failures, which are currently an issue – a temporary issue, I hope :unamused:-- where I live.

My computer gets power through a UPS, and I’ve always had time after these power failures to log out and shutdown properly. However, on reboot, the mysterious “Login failed” messages. I have had to “fix” the problem by restoring the Tumbleweed partition, which is time consuming.

I can still login to run level 3, and thought of copying related SDDM files to a separate directory while the computer is working properly, then restoring them after a power failure. However, I’m not sure what to copy. I tried copying the .conf files in /etc/sddm.conf.d and /usr/lib/sddm/sddm.conf.d, but restoring them didn’t fix the problem. Did I miss a directory or a configuration file?

FWIW: this problem would make a lot more sense to me if I didn’t have a UPS, and hadn’t had time to properly shutdown. I’m baffled by how a normal shutdown under UPS power would produce this problem.

2

Workaround: switch to LightDM. I have only one or two Plasma installations left using SDDM. I have several using LightDM, but mostly use either KDM3 or TDM, so X remains living on vtty7, and I have all of 1-6 remaining for my text logins.

3

I eventually may take you up on that suggestion, Felix, but I’d like to salvage SDDM if I can, if only for aesthetic reasons.

I see now that I also could have copied over the empty configuration file /etc/sddm.conf and the contents of /usr/share/sddm. I’ll try that if I suffer the same problem again.

I should have mentioned: I log in with Wayland, and could try to see if I can log in to an X11 after I see the ‘Failed login’ message.

4

Often the problem is that the disk/partition is near full.

Log into terminal or boot to external to look around

5

There’s lots of room in the partition, gogalthorp. Still, thanks for the feedback.

6

I STRONGLY ADVISE AGAINST USING THE METHOD BELOW!
But if the situation gets really dire, and there are no other options left, you could try this:

7

Thank you, asdhio.

8

Can you start plasma wayland from the console ? Switch to a tty, login and type startplasma-wayland .
If plasma start, it confirm there is a problem with sddm and plasma wayland… I have the same problem on Arch but only solution I found was to disable sddm and start myself the session I want.

9

I can give that a try if the problem strikes again, PerfMonk. Thank you. However, I think I’ve found a workaround – in my residence, and not in my OS – that is likely to prevent the problem from recurring.

10

Post your sddm.log to see what’s the problem!