SDDM Dual-Screen Need help setting default monitor on login

Desktop Environments Plasma
1

Hey there, I’m quite new to Linux and got the following question:
How do I setup a specific monitor as default on login via SDDM?

I’m running the latest EOS with KDE Plasma.
I’ve got two Monitors connected to DP-1 and DP-2, the Default Monitor is DP-2.

In this configuration my UEFI is shown on the default monitor, as is everything else that is not set up for dual-monitor-use like system.d or a Live-Linux, even Windows-Setup. They all default to DP-2.

The login-screen however doesn’t. On each screen there is an input field for the user-password, the one on DP-1 is active, the mouse pointer appears on DP-1 as well, the input field on DP-2 is inactive.

The funny part: When I enter my password on DP-1 it doesn’t login. The input field just gets inactive. To log into my computer I have to activate the input field on DP-2 and enter my pw there.

After logging in the default monitor is DP-2 again.

I’ve looked through several pages on the Arch-Wiki, but I got a little lost there. So my problem seems to be with sddm and X, since KDE-plasma uses Wayland and got nothing to do with the login-screen.

But how can I change the settings for sddm so it is permanently set on boot?

I tried setting it in system-settings → design → login-screen (sddm) → use plasma-settings with no effect.

As suggested at https://wiki.archlinux.org/title/SDDM#Match_Plasma_display_configuration I copied the kwinoutputconfig.json also with no effect.

I then tried to edit /usr/share/sddm/scripts/Xsetup like suggested at https://wiki.archlinux.org/title/SDDM#Login_session_appears_on_an_unexpected_display
But that mirrored DP-1 to both screens and I couldn’t login since the password-input-field just deactivated. I’m not sure which arguments I should use, maybe “–preferred” instead of “–auto”, or “–pos xy” instead of “right-of DP-2”

xrandr | grep -w connected

DP-2 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 598mm x 336mm
DP-1 connected 1920x1080+1920+0 (normal left inverted right x axis y axis) 598mm x 336mm

/usr/share/sddm/scripts/XSetup

#!/bin/sh
# Xsetup - run as root before the login dialog appears

xrandr --output DP-1 --right-of DP-2 --noprimary --auto
xrandr --output DP-2 --primary --auto

inxi -G

Graphics:
  Device-1: NVIDIA GA106 [RTX A2000 12GB] driver: nvidia v: 565.57.01
  Display: wayland server: X.org v: 1.21.1.14 with: Xwayland v: 24.1.4
    compositor: kwin_wayland driver: X: loaded: nvidia unloaded: modesetting
    gpu: nvidia resolution: 1: 1920x1080 2: 1920x1080
  API: EGL v: 1.5 drivers: nvidia,swrast
    platforms: gbm,wayland,x11,surfaceless,device
  API: OpenGL v: 4.6.0 compat-v: 4.5 vendor: nvidia mesa v: 565.57.01
    renderer: NVIDIA RTX A2000 12GB/PCIe/SSE2
  API: Vulkan v: 1.3.295 drivers: nvidia surfaces: xcb,xlib,wayland
2

Welcome to the community @Downer_Dan :wave: :sunglasses: :enos_flag:

Here are a couple of other topics you might look at for context and details:

Perhaps you might try switching off your second screen, just at SDDM login, seeing as only one will work at the moment when using the Breeze theme (established bug). Something like this:

/usr/share/sddm/scripts/XSetup

#!/bin/sh
# Xsetup - run as root before the login dialog appears

xrandr --output DP-2 --primary --auto
xrandr --output DP-1 --off
1 Like
3

Thank you,
as a quick-and-dirty-workaround I already did that, at least I don’t have to switch monitors that way.

There are still some hurdles to take when switching to Linux. It was my main OS up until the early 2000s, so I knew what I was getting into, but Win2k made my life a lot easier and I was a Win-only-user during the last 20 years. I still love Win10, but after MS announced the end of it and forced everyone to use their bloated-shitty-AI-privacy-nightmare-OS where you can’t even resize the taskbar anymore I knew I had to switch back.

Sometimes the possibilities in Linux are somewhat overwhelming to a new user, maybe I’ll leave it as is for now with DP-1 turned off. There is still a lot to (re-)learn.

Thank you very much for your help, your links helped me to understand the problem better.

4

I had the same problem as the OP. Your suggestion was the only way to get SDDM to only one display.

5

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