[SOLVED][KDE Plasma 6][Wayland] SDDM crashes on startup

virgilggx · 2026-02-07 10:49:51

Hello,

Since a recent update of my packages (unfortunately, I can't tell you which ones), I've been experiencing new problems, particularly when starting up the computer:

- When I log in with SDDM, the KDE Plasma session opens, the cursor appears, I can move it for about 2 seconds, then it freezes (the Plasma interface does not appear, there is only my wallpaper and the cursor), and I have to wait 8-10 minutes before the SDDM screen reappears and I can finally log in normally. I can't switch to TTY nor use Kernel Sysrq.

- Also, I am now unable to perform an administrator action on a GUI program by entering the correct password; the window displays the message: Authentication failure, please try again (exemple : pkexec ls). I don't have this problem with sudo.

Also, following this update, there have been two very strange behaviors:
- All my Firefox extensions have been disabled. (I have reactivated them).
- I had configured PowerDevil to limit the battery charge to 80%, but this has been disabled and I am unable to reactivate it (it asks me for the administrator password and does not recognize it).

And I still can't change the backlight on my computer screen (the brightness is fine), after trying different combinations of the parameters: acpi_backlight, amdgpu.backlight, nvidia.NVreg_EnableBacklightHandler, brightnessctl still changes the value correctly, but there is no change in the backlight.

I'm using 6.17.13-hardened1-2-hardened kernel.
With KDE Plasma 6 / SDDM / Wayland.
With drivers :

 yay -Qs amd
local/amd-ucode 20260110-1
    Microcode update image for AMD CPUs
local/distorm 3.5.2.b-5
    Powerful disassembler library for x86/AMD64
local/lib32-vulkan-radeon 1:25.3.4-1
    Open-source Vulkan driver for AMD GPUs - 32-bit
local/libteam 1.32-3
    Library for controlling team network device
local/linux-firmware-amdgpu 20260110-1
    Firmware files for Linux - Firmware for AMD Radeon GPUs
local/nvtop 3.3.1-1
    GPUs process monitoring for AMD, Intel and NVIDIA
local/vulkan-radeon 1:25.3.4-1
    Open-source Vulkan driver for AMD GPUs
local/xf86-video-amdgpu 25.0.0-1 (xorg-drivers)
    X.org amdgpu video driver

❯ yay -Qs nvidia
local/egl-gbm 1.1.3-1
    The GBM EGL external platform library
local/egl-wayland 4:1.1.21-1
    EGLStream-based Wayland external platform
local/egl-wayland2 1.0.0.rc.r57.g1893c37-1
    EGLStream-based Wayland external platform (2)
local/egl-x11 1.0.4-1
    NVIDIA XLib and XCB EGL Platform Library
local/ffnvcodec-headers 13.0.19.0-1
    FFmpeg version of headers required to interface with Nvidias codec APIs
local/lib32-nvidia-utils 590.48.01-1
    NVIDIA drivers utilities (32-bit)
local/libva-nvidia-driver 0.0.15-1
    VA-API implementation that uses NVDEC as a backend
local/libvdpau 1.5-3
    Nvidia VDPAU library
local/libxnvctrl 590.48.01-1
    NVIDIA NV-CONTROL X extension
local/linux-firmware-nvidia 20260110-1
    Firmware files for Linux - Firmware for NVIDIA GPUs and SoCs
local/nvidia-open-dkms 590.48.01-2
    NVIDIA open kernel modules - module sources
local/nvidia-prime 1.0-5
    NVIDIA Prime Render Offload configuration and utilities
local/nvidia-prime-rtd3pm 1.1-1
    Configure your discrete NVIDIA GPU to power down when not in use.
local/nvidia-settings 590.48.01-1
    Tool for configuring the NVIDIA graphics driver
local/nvidia-utils 590.48.01-2
    NVIDIA drivers utilities
local/nvtop 3.3.1-1
    GPUs process monitoring for AMD, Intel and NVIDIA

My boot logs: http://0x0.st/PcRI.txt
My kernel's parameters:

title Arch Linux (hardened)
linux /vmlinuz-linux-hardened
initrd /amd-ucode.img
initrd /initramfs-linux-hardened.img
options rd.luks.name=1732ae68-3bb0-4703-aa43-eeb554fbb863=cryptroot root=/dev/mapper/cryptroot rootflags=subvol=@ splash quiet rw audit=1 audit_backlog_limit=8192 kernel.sysrq=1 fsck.mode=force fsck.repair=yes lsm=landlock,lockdown,yama,integrity,apparmor,bpf ipv6.disable=1 nvidia-drm.modeset=1 nvidia_drm.fbdev=1 nvidia.NVreg_DynamicPowerManagement=0x03

My /etc/mkinitcpio.conf modules / hooks:

MODULES=(btrfs usbhid xhci_hcd amdgpu nvidia nvidia_modeset nvidia_uvm nvidia_drm)
HOOKS=(base systemd autodetect microcode modconf keyboard sd-vconsole block plymouth sd-encrypt filesystems fsck)

SDDM repeatedly spams the following message during the freeze: sddm-greeter[7637]: Error: "Internal data stream error."

In AppArmor logs:

[...]
ALLOWED polkit-kde-authentication-agent open /usr/share/sounds/ocean/stereo/dialog-warning-auth.oga comm=polkit-kde-auth requested_mask=r denied_mask=r
[...]

Can you help me?

[EDIT]
I tried to remove nvidia-drm.modeset=1 nvidia_drm.fbdev=1 from kernel's option line and Nvidia's module from initramfs but it doesn't change anything.
I also added export KWIN_DRM_DEVICES=/dev/dri/card1 into .bash_profile and same result.

Another strange thing is that when I log back in via SDDM (after the initial crash), the session opens with the programs from the previous session (even if I closed them).

Last edited by virgilggx (2026-02-14 08:24:28)

seth · 2026-02-07 16:01:28

févr. 07 10:50:27 ltp-arch-nayrosk systemd-logind[6689]: New session 'c1' of user 'sddm' with class 'greeter' and type 'wayland'.
févr. 07 10:50:29 ltp-arch-nayrosk sddm-greeter[7637]: Error: "Internal data stream error."

I also added export KWIN_DRM_DEVICES=/dev/dri/card1 into .bash_profile and same result.

Your users .bash_profile isn't sourced by sddm, but I assume you're trying to use kwin_wayland as wayland compositor for SDDM?

Does SDDM on X11 work as expected?

févr. 07 10:50:49 ltp-arch-nayrosk sddm-greeter[7637]: GStreamer; Unable to pause - "http://a1.v2.phobos.apple.com.edgesuite.net/us/r1000/000/Features/atv/AutumnResources/videos/b3-2.mov"

Is this somehow part of an animated wallpaper?

Then there's

févr. 07 10:51:45 ltp-arch-nayrosk plasmashell[87430]: MESA: error: ZINK: vkEnumeratePhysicalDevices failed (VK_ERROR_INITIALIZATION_FAILED)
févr. 07 10:51:45 ltp-arch-nayrosk plasmashell[87430]: MESA: error: ZINK: failed to choose pdev
févr. 07 10:51:45 ltp-arch-nayrosk plasmashell[87430]: libEGL warning: egl: failed to create dri2 screen

virgilggx · 2026-02-07 16:16:11

seth wrote:

Your users .bash_profile isn't sourced by sddm, but I assume you're trying to use kwin_wayland as wayland compositor for SDDM?

Yes, and it has been working until now:

❯ cat /etc/sddm.conf.d/10-display.conf
[General]
DisplayServer=wayland
GreeterEnvironment=QT_WAYLAND_SHELL_INTEGRATION=layer-shell

[Wayland]
CompositorCommand=kwin_wayland --drm --no-lockscreen --no-global-shortcuts --locale1

seth wrote:

Does SDDM on X11 work as expected?

I can't switch to X11 (I only have Wayland option in right left on SDDM screen).

seth wrote:

Is this somehow part of an animated wallpaper?

Yes, from Aerial SDDM Theme

Last edited by virgilggx (2026-02-07 16:44:07)

seth · 2026-02-07 16:31:03

Check your pacman.log, see whether the kernel or ddcutil were updated.
Deducing the data stream noise (which might really be just noise from the theme/wallpaper)

févr. 07 10:50:05 archlinux kernel: Linux version 6.17.13-hardened1-2-hardened (linux-hardened@archlinux) (gcc (GCC) 15.2.1 20260103, GNU ld (GNU Binutils) 2.45.1) #1 SMP PREEMPT_DYNAMIC Sat, 03 Jan 2026 21:47:05 +0000
févr. 07 10:50:27 ltp-arch-nayrosk systemd-logind[6689]: New session '1' of user 'sddm' with class 'manager-early' and type 'unspecified'.
févr. 07 10:51:36 ltp-arch-nayrosk systemd-logind[6689]: New session '2' of user 'nayrosk' with class 'user' and type 'wayland'.

SDDM starts after 22s and you log in 49s later - not exactly "fast" but a far cry from "8-10 minutes before the SDDM screen reappears"

févr. 07 10:50:10 archlinux kernel: nvidia 0000:01:00.0: [drm] Cannot find any crtc or sizes

Can you disable the nvidia GPU in your UEFI settings for a test?
Could also just be another case of https://bbs.archlinux.org/viewtopic.php … 8#p2256418

virgilggx · 2026-02-07 16:52:34

seth wrote:

Check your pacman.log, see whether the kernel or ddcutil were updated.]

https://pastebin.com/3eZrNAmh

seth wrote:

22s and you log in 49s later - not exactly "fast" but a far cry from "8-10 minutes before the SDDM screen reappears"]

Here's what's happening:
1. I start the computer and log in via SDDM
2. The session starts, the background appears, and so does the mouse cursor
3. I can move the cursor for 2 seconds, then it freezes and I can't do anything (switch to TTY doesn't work nor force reboot or kill process with sysrq)
4. About 9 minutes later, the screen turns off, and if I move the mouse, I appear on the SDDM login screen, where I can start the session

seth wrote:

Can you disable the nvidia GPU in your UEFI settings for a test?]

I tried, but I got the same result.

Last edited by virgilggx (2026-02-07 16:55:38)

seth · 2026-02-07 17:01:47

The most likely cause is ddcutil
https://bbs.archlinux.org/viewtopic.php?id=312039
https://bbs.archlinux.org/viewtopic.php?id=312019

virgilggx · 2026-02-07 17:23:17

seth wrote:

The most likely cause is ddcutil
https://bbs.archlinux.org/viewtopic.php?id=312039
https://bbs.archlinux.org/viewtopic.php?id=312019

Thanks, after disabling ddcutil, it works again.
However, I still have the problem with polkit, I don't know if it's related.

seth · 2026-02-07 17:35:35

unable to perform an administrator action on a GUI program by entering the correct password; the window displays the message: Authentication failure, please try again (exemple : pkexec ls)

Do you get a password dialog or are you asked for the password on the prompt?
Are there polkit related messages in the system journal?

On a formal note, in future please avoid omnibus threads and open one thread per issue.

virgilggx · 2026-02-07 19:26:54

seth wrote:

Do you get a password dialog or are you asked for the password on the prompt?

When I run, for example: pkexec id, I get a window to enter the password.

seth wrote:

Are there polkit related messages in the system journal??

Yes :

In AppArmor:

❯  aa-log
[...]
ALLOWED polkit-kde-authentication-agent open /usr/share/sounds/ocean/stereo/dialog-warning-auth.oga comm=polkit-kde-auth requested_mask=r denied_mask=r
[...]

And service's logs:

❯ journalctl -f -u polkit.service
févr. 07 18:18:06 ltp-arch-nayrosk systemd[1]: Starting Authorization Manager...
févr. 07 18:18:06 ltp-arch-nayrosk polkitd[5452]: Started polkitd version 127
févr. 07 18:18:06 ltp-arch-nayrosk systemd[1]: Started Authorization Manager.
févr. 07 18:19:12 ltp-arch-nayrosk polkitd[5452]: Operator of unix-session:2 FAILED to authenticate to gain authorization for action org.kde.powerdevil.chargethresholdhelper.setconservationmode for system-bus-name::1.89 [/usr/bin/systemsettings] (owned by unix-user:nayrosk)

The only related file I modified in connection with this is:

❯ sudo cat  /etc/security/faillock.conf
# Configuration for locking the user after multiple failed
# authentication attempts.
#
# The directory where the user files with the failure records are kept.
# The default is /var/run/faillock.
dir = /var/lib/faillock
#
# Will log the user name into the system log if the user is not found.
# Enabled if option is present.
audit
#
# Don't print informative messages.
# Enabled if option is present.
# silent
#
# Don't log informative messages via syslog.
# Enabled if option is present.
# no_log_info
#
# Only track failed user authentications attempts for local users
# in /etc/passwd and ignore centralized (AD, IdM, LDAP, etc.) users.
# The `faillock` command will also no longer track user failed
# authentication attempts. Enabling this option will prevent a
# double-lockout scenario where a user is locked out locally and
# in the centralized mechanism.
# Enabled if option is present.
# local_users_only
#
# Deny access if the number of consecutive authentication failures
# for this user during the recent interval exceeds n tries.
# The default is 3.
deny = 5
#
# The length of the interval during which the consecutive
# authentication failures must happen for the user account
# lock out is n seconds.
# The default is 900 (15 minutes).
# fail_interval = 900
#
# The access will be re-enabled after n seconds after the lock out.
# The value 0 has the same meaning as value `never` - the access
# will not be re-enabled without resetting the faillock
# entries by the `faillock` command.
# The default is 600 (10 minutes).
# unlock_time = 600
#
# Root account can become locked as well as regular accounts.
# Enabled if option is present.
# even_deny_root
#
# This option implies the `even_deny_root` option.
# Allow access after n seconds to root account after the
# account is locked. In case the option is not specified
# the value is the same as of the `unlock_time` option.
# root_unlock_time = 900
#
# If a group name is specified with this option, members
# of the group will be handled by this module the same as
# the root account (the options `even_deny_root` and
# `root_unlock_time` will apply to them).
# By default, the option is not set.
# admin_group = <admin_group_name>

And my user is in these groups:

❯ id
uid=1000(nayrosk) gid=1000(nayrosk) groups=1000(nayrosk),43(tor),946(audit),959(docker),998(wheel)

seth wrote:

On a formal note, in future please avoid omnibus threads and open one thread per issue.

Ok sorry.

[EDIT]

In log I read:

févr. 07 20:20:54 ltp-arch-nayrosk polkit-agent-helper-1[27272]: pam_unix(polkit-1:auth): conversation failed
févr. 07 20:20:54 ltp-arch-nayrosk polkit-agent-helper-1[27272]: pam_unix(polkit-1:auth): auth could not identify password for [nayrosk]
févr. 07 20:20:54 ltp-arch-nayrosk polkit-agent-helper-1[27272]: pam_faillock(polkit-1:auth): Error opening the tally file for nayrosk: Read-only file system

And

❯ sudo ls -l /var/lib/faillock/
total 0
-rw-rw---- 1 nayrosk root 0  7 févr. 20:46 nayrosk
-rw-rw---- 1 root    root 0  6 févr. 10:08 root

Last edited by virgilggx (2026-02-07 19:49:47)

seth · 2026-02-07 20:40:27

findmnt -t /var/lib/faillock

but the log complaint also seems to predate the timestamp.
Can you query

faillock

?

Arch Linux

#1 2026-02-07 10:49:51

[SOLVED][KDE Plasma 6][Wayland] SDDM crashes on startup

#2 2026-02-07 16:01:28

Re: [SOLVED][KDE Plasma 6][Wayland] SDDM crashes on startup

#3 2026-02-07 16:16:11

Re: [SOLVED][KDE Plasma 6][Wayland] SDDM crashes on startup

#4 2026-02-07 16:31:03

Re: [SOLVED][KDE Plasma 6][Wayland] SDDM crashes on startup

#5 2026-02-07 16:52:34

Re: [SOLVED][KDE Plasma 6][Wayland] SDDM crashes on startup

#6 2026-02-07 17:01:47

Re: [SOLVED][KDE Plasma 6][Wayland] SDDM crashes on startup

#7 2026-02-07 17:23:17

Re: [SOLVED][KDE Plasma 6][Wayland] SDDM crashes on startup

#8 2026-02-07 17:35:35

Re: [SOLVED][KDE Plasma 6][Wayland] SDDM crashes on startup

#9 2026-02-07 19:26:54

Re: [SOLVED][KDE Plasma 6][Wayland] SDDM crashes on startup

#10 2026-02-07 20:40:27

Re: [SOLVED][KDE Plasma 6][Wayland] SDDM crashes on startup

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