this post was submitted on 13 Oct 2025
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Kubuntu - SDDM not loading (lemmy.sdf.org)
submitted 1 month ago* (last edited 1 month ago) by RubberDuckyDJ@lemmy.sdf.org to c/linux@programming.dev
11 comments fedilink hide all child comments
 

At first Instead of my SDDM I would just see an after image of what was last displayed on screen. But if I typed in my password and pressed enter, it would let me in just fine. Then after following some suggestions from users in r/Kubuntu I’ve made a bit of progress. Now when I boot up my computer instead of the SDDM being invisible, it now doesn’t load at all, from there I switch to tty3 then back to tty2 and then log in through the terminal. After that I run startplasma-wayland and then I have access to my desktop. The post where all this went down - https://www.reddit.com/r/Kubuntu/comments/1nvreuo/sddm_not_rendering/

Does anyone know a fix? I would like to be able to see my login screen.

Here’s my specs in case that would help - https://i.imgur.com/XtC43zw.png

And here’s my journalctl output after booting and launching plasma - https://pastebin.com/nnGsWebd

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[–] A_norny_mousse@feddit.org 3 points 1 month ago (1 children)

Your journal output might be too curated, I don't see anything that would keep the display manager from starting up.

Then after following some suggestions from users in r/Kubuntu I’ve made a bit of progress.

We'd need more info on this, like what exactly did you change and what was that progress and how/when did it turn into regress.

Journal output for SDDM and related services, and for the relevant timeframe, would be better.

I suppose SDDM is the default for Kubuntu, and if you had done other possibly relevant things to your setup you'd have told us.

FWIW, it could be GPU related, but that really just is a wild guess.

PS: identical post here: https://lemmy.sdf.org/post/43982607

[–] Successful_Try543@feddit.org 2 points 1 month ago* (last edited 1 month ago) (1 children)

Your journal output might be too curated, I don't see anything that would keep the display manager from starting up.

The only suspicious entry I've found was #185:

sddm[1596]: Failed to read display number from pipe

FWIW, it could be GPU related, but that really just is a wild guess.

Skimming search results onto the above error message seems to second your idea.

[–] A_norny_mousse@feddit.org 1 points 1 month ago (1 children)

👍 I missed that one. Yeah, OP should at least look what else is happening around that.

[–] RubberDuckyDJ@lemmy.sdf.org 1 points 1 month ago (1 children)

The issue is I have no idea what any of these errors mean. I'm pretty new to desktop Linux so I've just been researching the errors one by one but so far, no dice.

[–] A_norny_mousse@feddit.org 2 points 1 month ago (1 children)

Show us! The journalctl output was too restricted, we need to see all of it - at least for the significant timeframe.

[–] RubberDuckyDJ@lemmy.sdf.org 2 points 1 month ago (1 children)

Alr here's all of it. Sorry that took so long. https://drive.google.com/file/d/1bocHEulCDEKUIradHJPTxwI84ZDJcuX9

[–] A_norny_mousse@feddit.org 2 points 1 month ago* (last edited 1 month ago) (1 children)

Not downloading and reading 181MB of logs. You probably used journalctl without any qualifiers, right?

What we want is

  1. The current boot showed the erroneous behavior
  2. Make note of the timeframe the erroneous behavior occured

Compose a journalctl command that takes these aspects into account, i.e.:

journalctl --boot --since <date_time> --until <date_time>

Also see:

-S, --since=, -U, --until=
   Start showing entries on or newer than the specified date, or on
   or older than the specified date, respectively. Date
   specifications should be of the format "2012-10-30 18:17:16". If
   the time part is omitted, "00:00:00" is assumed. If only the
   seconds component is omitted, ":00" is assumed. If the date
   component is omitted, the current day is assumed. Alternatively
   the strings "yesterday", "today", "tomorrow" are understood,
   which refer to 00:00:00 of the day before the current day, the
   current day, or the day after the current day, respectively.
   "now" refers to the current time. Finally, relative times may be
   specified, prefixed with "-" or "+", referring to times before or
   after the current time, respectively. For complete time and date
   specification, see systemd.time(7). Note that --output=short-full
   prints timestamps that follow precisely this format.

Assuming 1. and 2. are in effect, you can also try this:

systemctl status -n999 sddm
[–] RubberDuckyDJ@lemmy.sdf.org 2 points 1 month ago (1 children)

journalctl --boot --since "2025-10-15 8:18:00" --until "2025-10-15 8:21:00" --no-tail > log.log

https://drive.google.com/file/d/1syk9Okhq7qA3TLMxNpO-35JmmKFKWIaW

systemctl status -n999 sddm

https://pastebin.com/mF9h0x9e

Hope I did this right.

[–] A_norny_mousse@feddit.org 2 points 1 month ago* (last edited 1 month ago) (1 children)

Neither output shows the string "Failed to read display number from pipe".

Why?

FWIW, the journal snippet shows a mostly healthy KDE session has started, no errors.

It's up to you to provide some context now.

[–] RubberDuckyDJ@lemmy.sdf.org 2 points 1 month ago (1 children)

Here is a video I recorded of what it looks like to log into my conputer from boot.

https://drive.google.com/file/d/1xX0xYuefGoGZ1ddW5fOG6GPkUThfvE6B/

I genuinely don't know how to describe this since I don't entirely understand what is actually going on here.

[–] A_norny_mousse@feddit.org 2 points 1 month ago* (last edited 1 month ago)

I see. That's why it doesn't show up as an error, presuming you got the instructions from my previous post correct (that the problem actually occured in the timeframe given) - sddm is apparently oblivious to the problem.

Searching "kubuntu sddm blank screen" gives some relevant-looking forum posts; I found these to be good reading:

https://bbs.archlinux.org/viewtopic.php?id=226363 => content of /etc/sddm.conf please
https://www.kubuntuforums.net/forum/newbie-support/help-the-new-guy/68489-sddm-black-screen-but-working-somewhat

They should give you some idea where to go from here.

Since this topic has been going on for a while, to no avail, I will lecture you now:

  • asking for help requires you to remain an active participant, i.e. we find the solution together. Actually, you have to put in more effort than the people helping you because you are the only one with access to the machine. This includes going through each comment again and again. It's your job to keep the overview, aggregate and evaluate all info and progress.
  • IMHO a branching tree of comments veering off topic is not a good medium to find a solution to a single technical problem. A linear format is better suited, like a forum.
  • Double posting, as you probably realized by now, makes it all even messier.