[SOLVED] Issue starting Plasma / Sddm

SpeedLight1221 · 2025-11-15 15:22:34

Hello.

Yesterday I installed plasma and uninstalled gnome. Everything went smoothly. Today i tried booting into Arch, but i ended up with a black screen. It seems that sddm either failed to start plasma or failed to run itself.

After selecting Arch Linux in grub, it showed me "loading linux lts" and something with ramdisk. After that the normal arch boot process log screen. Then the black screen. I Tried opening a terminal with "CTRL+ALT+F(1-6) but with no success.
I had to edit the start commands in grub and add "multi-user.target". After that it booted with a terminal, allowing me to log in and start plasma manually.

However, before i did that, i tried using the "Advanced options for arch" in grub. Selecting either Linux lts or Linux in the advanced options worked normally with plasma loading as it should.

I tried adding "Session=plasma" and "user=speedlight" into the autologin section of "/etc/sddm.conf.d/kde_settings.conf" without success.
There is a file "/etc/sddm.conf which is completely empty, but from what i understood that shouldn't be an issue.

Here is the sddm journal log from when i attempted to boot normally, resulting in a black screen.

-- Boot bb780b11d6e447e28ddd885f293a6d40 --
Nov 15 15:22:37 archlinux systemd[1]: Started Simple Desktop Display Manager.
Nov 15 15:22:37 archlinux sddm[753]: Initializing...
Nov 15 15:22:37 archlinux sddm[753]: Starting...
Nov 15 15:22:37 archlinux sddm[753]: Logind interface found
Nov 15 15:22:37 archlinux sddm[753]: Adding new display...
Nov 15 15:22:37 archlinux sddm[753]: Loaded empty theme configuration
Nov 15 15:22:37 archlinux sddm[753]: Xauthority path: "/run/sddm/xauth_uhfrfM"
Nov 15 15:22:37 archlinux sddm[753]: Using VT 2
Nov 15 15:22:37 archlinux sddm[753]: Display server starting...
Nov 15 15:22:37 archlinux sddm[753]: Writing cookie to "/run/sddm/xauth_uhfrfM"
Nov 15 15:22:37 archlinux sddm[753]: Running: /usr/bin/X -nolisten tcp -background none -seat seat0 vt2 -auth /run/sddm/xauth_uhfrfM -noreset -displayfd 16
Nov 15 15:22:39 archlinux sddm[753]: Setting default cursor
Nov 15 15:22:39 archlinux sddm[753]: Could not setup default cursor
Nov 15 15:22:39 archlinux sddm[753]: Running display setup script  "/usr/share/sddm/scripts/Xsetup"
Nov 15 15:22:39 archlinux sddm[753]: Display server started.
Nov 15 15:22:39 archlinux sddm[753]: Socket server starting...
Nov 15 15:22:39 archlinux sddm[753]: Socket server started.
Nov 15 15:22:39 archlinux sddm[753]: Loading theme configuration from "/usr/share/sddm/themes/breeze/theme.conf"
Nov 15 15:22:39 archlinux sddm[753]: Greeter starting...
Nov 15 15:22:39 archlinux sddm-helper[770]: [PAM] Starting...
Nov 15 15:22:39 archlinux sddm-helper[770]: [PAM] Authenticating...
Nov 15 15:22:39 archlinux sddm-helper[770]: [PAM] returning.
Nov 15 15:22:39 archlinux sddm-helper[770]: pam_unix(sddm-greeter:session): session opened for user sddm(uid=959) by (uid=0)
Nov 15 15:22:39 archlinux sddm-helper[770]: Writing cookie to "/tmp/xauth_RnSaYW"
Nov 15 15:22:39 archlinux sddm-helper[770]: Starting X11 session: "" "/usr/bin/sddm-greeter-qt6 --socket /tmp/sddm-:0-fwmkuC --theme /usr/share/sddm/themes/breeze"
Nov 15 15:22:39 archlinux sddm[753]: Greeter session started successfully
Nov 15 15:22:39 archlinux sddm[753]: Message received from greeter: Connect
Nov 15 15:22:47 archlinux sddm[753]: Message received from greeter: Login
Nov 15 15:22:47 archlinux sddm[753]: Reading from "/usr/share/wayland-sessions/plasma.desktop"
Nov 15 15:22:47 archlinux sddm[753]: Session "/usr/share/wayland-sessions/plasma.desktop" selected, command: "/usr/lib/plasma-dbus-run-session-if-needed /usr/bin/startplasma-wayland" for VT 1
Nov 15 15:22:47 archlinux sddm-helper[843]: [PAM] Starting...
Nov 15 15:22:47 archlinux sddm-helper[843]: [PAM] Authenticating...
Nov 15 15:22:47 archlinux sddm-helper[843]: [PAM] Preparing to converse...
Nov 15 15:22:47 archlinux sddm-helper[843]: [PAM] Conversation with 1 messages
Nov 15 15:22:47 archlinux sddm-helper[843]: pam_kwallet5(sddm:auth): pam_kwallet5: pam_sm_authenticate
Nov 15 15:22:47 archlinux sddm-helper[843]: [PAM] returning.
Nov 15 15:22:47 archlinux sddm[753]: Authentication for user  "speedlight"  successful
Nov 15 15:22:47 archlinux sddm-helper[843]: pam_kwallet5(sddm:setcred): pam_kwallet5: pam_sm_setcred
Nov 15 15:22:47 archlinux sddm-helper[843]: pam_unix(sddm:session): session opened for user speedlight(uid=1000) by speedlight(uid=0)
Nov 15 15:22:47 archlinux sddm[753]: Auth: sddm-helper exited successfully
Nov 15 15:22:47 archlinux sddm[753]: Greeter stopped. SDDM::Auth::HELPER_SUCCESS
Nov 15 15:22:47 archlinux sddm-helper[843]: pam_kwallet5(sddm:session): pam_kwallet5: pam_sm_open_session
Nov 15 15:22:47 archlinux sddm-helper[843]: Starting Wayland user session: "/usr/share/sddm/scripts/wayland-session" "/usr/lib/plasma-dbus-run-session-if-needed /usr/bin/startplasma-wayland"
Nov 15 15:22:48 archlinux sddm[753]: Session started true
Nov 15 15:35:07 archlinux sddm[753]: Authentication error: SDDM::Auth::ERROR_INTERNAL "Process crashed"
Nov 15 15:35:07 archlinux sddm[753]: Auth: sddm-helper (--socket /tmp/sddm-auth-c96303c0-2f41-4beb-bb10-211143044469 --id 1 --start /usr/lib/plasma-dbus-run-session-if-needed /usr/bin/startplasma-wayland --user speedlight) crashed (exit code 1)
Nov 15 15:35:07 archlinux sddm[753]: Authentication error: SDDM::Auth::ERROR_INTERNAL "Process crashed"
Nov 15 15:35:07 archlinux sddm[753]: Auth: sddm-helper exited with 1
Nov 15 15:35:07 archlinux sddm[753]: Signal received: SIGTERM
Nov 15 15:35:07 archlinux systemd[1]: Stopping Simple Desktop Display Manager...
Nov 15 15:35:07 archlinux sddm[753]: Socket server stopping...
Nov 15 15:35:07 archlinux sddm[753]: Socket server stopped.
Nov 15 15:35:07 archlinux sddm[753]: Display server stopping...
Nov 15 15:35:08 archlinux sddm[753]: Display server stopped.
Nov 15 15:35:08 archlinux sddm[753]: Running display stop script  QList("/usr/share/sddm/scripts/Xstop")
Nov 15 15:35:08 archlinux systemd[1]: sddm.service: Deactivated successfully.
Nov 15 15:35:08 archlinux systemd[1]: Stopped Simple Desktop Display Manager.
Nov 15 15:35:08 archlinux systemd[1]: sddm.service: Consumed 3.170s CPU time, 443.3M memory peak.

And here is the log for when i added the multi-user.taget option and then started plasma manually

Nov 15 15:35:33 archlinux systemd[1]: Started Simple Desktop Display Manager.
Nov 15 15:35:33 archlinux sddm[713]: Initializing...
Nov 15 15:35:33 archlinux sddm[713]: Starting...
Nov 15 15:35:33 archlinux sddm[713]: Logind interface found
Nov 15 15:35:33 archlinux sddm[713]: Adding new display...
Nov 15 15:35:33 archlinux sddm[713]: Loaded empty theme configuration
Nov 15 15:35:33 archlinux sddm[713]: Xauthority path: "/run/sddm/xauth_BkpBbR"
Nov 15 15:35:33 archlinux sddm[713]: Using VT 2
Nov 15 15:35:33 archlinux sddm[713]: Display server starting...
Nov 15 15:35:33 archlinux sddm[713]: Writing cookie to "/run/sddm/xauth_BkpBbR"
Nov 15 15:35:33 archlinux sddm[713]: Running: /usr/bin/X -nolisten tcp -background none -seat seat0 vt2 -auth /run/sddm/xauth_BkpBbR -noreset -displayfd 16
Nov 15 15:35:35 archlinux sddm[713]: Setting default cursor
Nov 15 15:35:35 archlinux sddm[713]: Could not setup default cursor
Nov 15 15:35:35 archlinux sddm[713]: Running display setup script  "/usr/share/sddm/scripts/Xsetup"
Nov 15 15:35:35 archlinux sddm[713]: Display server started.
Nov 15 15:35:35 archlinux sddm[713]: Reading from "/usr/local/share/wayland-sessions/plasma.desktop"
Nov 15 15:35:35 archlinux sddm[713]: Reading from "/usr/share/wayland-sessions/plasma.desktop"
Nov 15 15:35:35 archlinux sddm[713]: Session "/usr/share/wayland-sessions/plasma.desktop" selected, command: "/usr/lib/plasma-dbus-run-session-if-needed /usr/bin/startplasma-wayland" for VT 1
Nov 15 15:35:35 archlinux sddm-helper[735]: [PAM] Starting...
Nov 15 15:35:35 archlinux sddm-helper[735]: [PAM] Authenticating...
Nov 15 15:35:35 archlinux sddm-helper[735]: pam_kwallet5(sddm-autologin:auth): pam_kwallet5: pam_sm_authenticate
Nov 15 15:35:35 archlinux sddm-helper[735]: pam_kwallet5(sddm-autologin:auth): pam_kwallet5: Couldn't get password (it is empty)
Nov 15 15:35:35 archlinux sddm-helper[735]: [PAM] Preparing to converse...
Nov 15 15:35:35 archlinux sddm-helper[735]: [PAM] Conversation with 1 messages
Nov 15 15:35:35 archlinux sddm-helper[735]: pam_kwallet5(sddm-autologin:auth): pam_kwallet5: Empty or missing password, doing nothing
Nov 15 15:35:35 archlinux sddm-helper[735]: [PAM] returning.
Nov 15 15:35:35 archlinux sddm[713]: Authentication for user  "speedlight"  successful
Nov 15 15:35:35 archlinux sddm-helper[735]: pam_kwallet5(sddm-autologin:setcred): pam_kwallet5: pam_sm_setcred
Nov 15 15:35:35 archlinux sddm-helper[735]: pam_unix(sddm-autologin:session): session opened for user speedlight(uid=1000) by speedlight(uid=0)
Nov 15 15:35:35 archlinux sddm-helper[735]: pam_kwallet5(sddm-autologin:session): pam_kwallet5: pam_sm_open_session
Nov 15 15:35:35 archlinux sddm-helper[735]: pam_kwallet5(sddm-autologin:session): pam_kwallet5: open_session called without kwallet5_key
Nov 15 15:35:35 archlinux sddm-helper[735]: Starting Wayland user session: "/usr/share/sddm/scripts/wayland-session" "/usr/lib/plasma-dbus-run-session-if-needed /usr/bin/startplasma-wayland"
Nov 15 15:35:36 archlinux sddm[713]: Session started true

This isn't too much of a problem but it is annoying.

Any any help is appreciated. Thanks

Last edited by SpeedLight1221 (2025-11-17 20:48:16)

seth · 2025-11-15 21:51:14

Don't filter the journal, from the symptoms the problem might be the greeter.

https://wiki.archlinux.org/title/Systemd#Drop-in_files
Edit sddm.service and add

ExecStartPre=/usr/bin/sleep 3

Does that help?

SpeedLight1221 · 2025-11-17 17:35:08

seth wrote:

Don't filter the journal, from the symptoms the problem might be the greeter.
https://wiki.archlinux.org/title/Systemd#Drop-in_files
Edit sddm.service and add
ExecStartPre=/usr/bin/sleep 3
Does that help?

Today i finally got time to try and fix this but it started without any issues. I will keep this in mind if it happens again. Thank you

seth · 2025-11-17 19:46:23

Since this is probably a race condition it's not implausible to be non-deterministic.

Please always remember to mark resolved threads by editing your initial posts subject - so others will know that there's no task left, but maybe a solution to find.
Thanks.

Arch Linux

#1 2025-11-15 15:22:34

[SOLVED] Issue starting Plasma / Sddm

#2 2025-11-15 21:51:14

Re: [SOLVED] Issue starting Plasma / Sddm

#3 2025-11-17 17:35:08

Re: [SOLVED] Issue starting Plasma / Sddm

#4 2025-11-17 19:46:23

Re: [SOLVED] Issue starting Plasma / Sddm

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