SDDM launching slowly, sometimes fails

Scaatis · 2025-04-28 10:15:49

For my recently setup system, I am using KDE Plasma with SDDM. I noticed that SDDM takes several seconds to start, I see a terminal cursor during that time, first blinking, then static. This is after the plymouth splash has cleared.

I thought this might be due to the "breeze" theme, maybe it is really heavy. I tried switching to "maldives", but then SDDM doesn't start at all. I get the blinking cursor, then static cursor, forever. I can switch to the other tty and log in the console, but SDDM did not start.

This is the content of /etc/sddm.conf.d/kde_settings.conf, which is the only config file in /etc/sddm.conf.d. /etc/sddm.conf exists, but is empty.

[Autologin]
Relogin=false
Session=
User=

[General]
HaltCommand=/usr/bin/systemctl poweroff
Numlock=on
RebootCommand=/usr/bin/systemctl reboot

[Theme]
Current=breeze
CursorTheme=breeze_cursors
Font=Noto Sans,10,-1,0,400,0,0,0,0,0,0,0,0,0,0,1

[Users]
MaximumUid=60513
MinimumUid=1000

I set these settings with sddm-kcm. Note that I also used the button "Apply Plasma Settings" from within kcm. The only evidence of that which I see in the config file is the cursor theme, I don't know if it edited anything else.

Here is the output of

journalctl -b | grep sddm

gist

I also had the same problem of SDDM not starting intermittently with the breeze theme, but since I am still in the process of setting up the system, any number of things could have caused that. In this case, I have a simple, reproducible setting that breaks it, so maybe that can help figuring out what's wrong.

seth · 2025-04-28 20:09:19

Grepping for sddm won't do - there's not much hinting at problems (except the failing case has the sddm helper exit w/ 127, EKEYEXPIRED? Most likely because the session terminated beforehand)

Please post your complete system journal for the boot:

sudo journalctl -b | curl -F 'file=@-' 0x0.st

Please post your Xorg log, https://wiki.archlinux.org/title/Xorg#General

and I'd highly recommend to disable plymouth and remove the quiet kernel parameter, so you can actually see what's going on.

Scaatis · 2025-04-29 10:10:48

Sure, here is the journal for the successful case: https://0x0.st/8WxJ.txt and the xorg log: https://0x0.st/8Wxy.txt

Hm, I see a lot of NVIDIA in that xorg log. This is a laptop with NVidia GPU and AMD Ryzen with Radeon iGPU. I would prefer the normal GUI stuff to run on iGPU. In my plasma (wayland) session, that seems to work.

Journal for the failed case: https://0x0.st/8Wxv.txt and xorg log: https://0x0.st/8Wxw.txt

I see a lot of driver module load errors in both logs. Could that be the cause of the delay? But it doesn't explain the failure to start at all in the second case.

Re: Plymouth. I already disabled plymouth and splash before, but it doesn't really help. There are hundreds of messages flying by in a few seconds, and during the time of interest, there is no log output on the screen, regardless of plymouth or splash, only a blinking and then freezing cursor. So if plymouth does not change what goes into the journal, I don't think it makes a difference here?

Last edited by Scaatis (2025-04-29 10:14:41)

seth · 2025-04-29 20:25:30

Wild guess, add "nvidia_drm.modeset=1" to the https://wiki.archlinux.org/title/Kernel_parameters to block the simpledrm device and restore the normal card order.

This has been a problem, but idk whether SDDM qualifies for the pattern (mostly whether it utilizes QtWebEngine)

ldd /usr/bin/sddm-greeter-qt6 | grep -i web

There's otherwise nothing revealing in the jorunals and no problems in the Xorg logs at all.
But in any event switch back to the breeze theme (as apparently maldives maybe makes it worse)

Scaatis · 2025-04-30 07:49:59

I have tried two workarounds:

Setting up SDDM to use Wayland instead of xorg. I'm using Wayland for plasma and have no intention of fiddling with xorg. Startup time is a little better, I haven't tested the Maldives theme yet.

Setting sddm to auto login - should that cause it not to start a session as no UI is rendered? There is still a short period with a blank screen and cursor. Maybe that is just Wayland (for the plasma session, not for SDDM) starting up?

Re nvidia_drm.modeset=1: It was my understanding that this was the default now?
It also seems like all these articles are assuming I *want* to in use the Nvidia driver during boot up, whereas I actually don't, I want to use the igpu. How would I configure that?

seth · 2025-04-30 12:45:21

Re nvidia_drm.modeset=1: It was my understanding that this was the default now?

seth wrote:

add "nvidia_drm.modeset=1" to the https://wiki.archlinux.org/title/Kernel_parameters to block the simpledrm device and restore the normal card order

*only* the kernel parameter does that as side-effect-hack, in addition you could try to remove the kms hook and explcitly add amdgpu to the MODULES array

Scaatis · 2025-04-30 19:22:44

Re nvidia_drm.modeset=1: I have not set this parameter, but cat /sys/module/nvidia_drm/parameters/modeset says Y. Are you saying that explicitly setting this parameter will have some additional effect?

I have made some progress: Installing xf86-video-amdgpu has introduced the iGPU to Xorg and it does appear to be loaded first. However, now the log looks like it's starting both?

http://0x0.st/84st.txt

Removing kms and adding amdgpu seems to have had no appreciable effect, individually or in combination.

Also, the blank screen with blinking cursor has not become faster. It seems to have become longer.

Edit: False alarm on that last one. Removing kms from mkinitcpio hooks broke plymouth. Somehow it did not fall back to text mode as it should and was instead treating me to another blinky cursor. Adding it back in fixed that.

I think I will stop messing with this for now. My solution is
1) Switch sddm to wayland, as that seems to start up faster
2) Autologin + instantly lock KDE session, which gives a smoother experience because the UI is already loaded when you enter the password

Last edited by Scaatis (2025-04-30 20:13:25)

seth · 2025-04-30 19:50:19

Are you saying that explicitly setting this parameter will have some additional effect?

Yes, that's the whole point here.
Normally the IGP will be card0 and the GPU card1, but w/ the simpledrm device transitionally occupying card0, the IGP will become card1 and the GPU takes the card0 slot after the IGP unloaded the simpledrm device.

Electron/Blink is otr to lose it over that, the sddm greeter is crashing. It the sddm greeter utilizes qtwebengine, it might be subject to the same condition.

Both cards have been picked up all the time and the server ran on the IGP all the time, that's normal for Optimus/PRIME

Arch Linux

#1 2025-04-28 10:15:49

SDDM launching slowly, sometimes fails

#2 2025-04-28 20:09:19

Re: SDDM launching slowly, sometimes fails

#3 2025-04-29 10:10:48

Re: SDDM launching slowly, sometimes fails

#4 2025-04-29 20:25:30

Re: SDDM launching slowly, sometimes fails

#5 2025-04-30 07:49:59

Re: SDDM launching slowly, sometimes fails

#6 2025-04-30 12:45:21

Re: SDDM launching slowly, sometimes fails

#7 2025-04-30 19:22:44

Re: SDDM launching slowly, sometimes fails

#8 2025-04-30 19:50:19

Re: SDDM launching slowly, sometimes fails

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