[Solved] How to reconfigure dual monitor setup on Debian 12?

[cephalopod_spider]

Hello! I have recently installed Debian 12 to dual boot with Windows 11, and had it set to my display configuration at the time of installation. I moved my computer to another room this week and swapped the displays position, then I entered the Gnome Classic Settings and changed the display position there too. The issue is that whenever I turn my PC on, the old display config still runs on the login screen, and when I log into my user it glitches out for a couple of seconds before returning to normal. I tried changing the display environment do Gnome, Gnome Classic on Wayland, and XFCE, where in all of them the display config was still the old one, so it seems there is some underlying configuration that I'm not being able to change.

I have very basic Linux knowledge in general, so I would very much appreciate if someone could help me find this file that I need to change in order to solve this. I saw a few posts mentioning a gdm3 directory in the /var/ and /etc/ directories, saying that I should copy my monitors.xml file found in my ~/.config/ directory to them, but it was a Ubuntu specific solution and it did not work. My thanks to whoever can help me!

[FreewheelinFrank]

I moved my computer to another room this week and swapped the displays position, then I entered the Gnome Classic Settings and changed the display position there too.

Just to be clear, this is the same monitor, right? By "swapped the position" do you mean horizontal to vertical or vice versa? Is the orientation wrong? A photo might help.

[cephalopod_spider]

Basically, my monitors were side by side, with the larger one on the left and the smaller on the right, then I swapped them to place the larger one on the right and the smaller on the left, but in the login screen it's still as if the larger one was in the left. I'm not home right now, when I get there I'll show the glitch on the screen when I login.

[cephalopod_spider]

Here's the screen glitch:

[FreewheelinFrank]

I've never used more than one screen, so excuse the stupid question. Are there sockets for primary/secondary monitor on the computer? I presume you swapped the connectors over?

It might help to edit the post title to get the attention of our multi-monitor-members. Something like "How to swap primary monitor on dual monitor setup" or "How to reconfigure dual monitor setup"?

[mrmazda]

What does inxi -GSaz --vs report?

[cephalopod_spider]

Firstly, there are no primary or secondary entrances. My motherboard is very simple. so I use the smaller monitor on VGA and the larger one on HDMI. The VGA one is always considered Display 1 by the OS and is the monitor where the BIOS is shown.

I will try and change the post name in order to gather more attention.

Secondly, here's what that command returns on Graphics:

Code: Select all

 Device-1: AMD Picasso/Raven 2 [Radeon Vega Series / Radeon Mobile Series]
    vendor: ASUSTeK driver: amdgpu v: kernel arch: GCN-5 code: Vega
    process: GF 14nm built: 2017-20 pcie: gen: 3 speed: 8 GT/s lanes: 16
    ports: active: DP-1,HDMI-A-1 empty: DVI-D-1 bus-ID: 08:00.0
    chip-ID: 1002:15d8 class-ID: 0300 temp: 46.0 C
  Display: x11 server: X.Org v: 1.21.1.7 with: Xwayland v: 22.1.9
    compositor: gnome-shell driver: X: loaded: amdgpu
    unloaded: fbdev,modesetting,vesa dri: radeonsi gpu: amdgpu display-ID: :0
    screens: 1
  Screen-1: 0 s-res: 3286x1080 s-dpi: 96 s-size: 869x285mm (34.21x11.22")
    s-diag: 915mm (36.01")
  Monitor-1: DP-1 mapped: DisplayPort-0 pos: bottom-l model: AOC 1670W
    serial: <filter> built: 2019 res: 1366x768 hz: 60 dpi: 101 gamma: 1.2
    size: 344x194mm (13.54x7.64") diag: 395mm (15.5") ratio: 16:9 modes:
    max: 1366x768 min: 720x400
  Monitor-2: HDMI-A-1 mapped: HDMI-A-0 pos: primary,top-right
    model: AOC 24B1W1G5 serial: <filter> built: 2022 res: 1920x1080 hz: 60
    dpi: 93 gamma: 1.2 size: 527x296mm (20.75x11.65") diag: 604mm (23.8")
    ratio: 16:9 modes: max: 1920x1080 min: 720x400
  API: OpenGL v: 4.6 Mesa 22.3.6 renderer: AMD Radeon Vega 11 Graphics
    (raven LLVM 15.0.6 DRM 3.49 6.1.0-18-amd64) direct-render: Yes 

I don't know how to interpret any of that, but I hope it helps!

[mrmazda]

Whenever copying and pasting command output, please use the </> icon above the input window to place code tags before and after what you paste. This preserves the original formatting of the command output. Your paste within should include the command line used and the following shell prompt, so that we can be sure of what we are seeing. The code tags may be typed in manually if you prefer, and you are free to edit post #7 to include them.

Another screenshot might help, one showing the login greeter screen on the "wrong" display. Your inxi output is showing an over/under display positioning, with the larger as primary on top. Based on the rectangles on your larger display, it is apparently being improperly handled by whatever is supposed to be controlling your login screens' layout.

We don't know which DM you are using. I should have suggested inxi -GSaz rather than inxi -Gaz, which would have included that bit of info. Except for that bit, we shouldn't have use for any of what else -S provides.

I never use GDM, so if that's what you're using, I can't be of more specifiic help. I have only 2 or 3 out of 100+ installations using SDDM, so can't really help with it either. I think there should be either an /etc/sddm/ or /etc/sddm.conf or /etc/sddm.conf.d/ that can be reconfigured to designate a primary. If using LightDM, then there may be an optional file in place /etc/lightdm/lightdm.conf that can be used to designate which display is the primary. /etc/lightdm/ may have another file *-greeter.conf. It appears possibly it (lightdm-gtk-greeter.conf here on an openSUSE installation) can control position via active-monitor =.

On my multi-display PCs I don't ordinarily try to designate a primary, as all are in use and suitable for use for the login screen. All of my Debian installations use TDM, where tdmrc can designate a specific display be used for login. I normally don't bother designating a primary, instead being satisfied with whatever turns out to be the greeter screen, and designating the primary for desktop sessions via an xrandr script in /etc/Xsession.d/, which applies regardless of DE or WM session selected. Which display driver is in use can affect which is used - the login area sometimes appears on multiple displays.

[cephalopod_spider]

I will take note on the code formatting, thank you.

The issue is not about a primary/secondary monitor, the issue is that the computer thinks that the displays are not where they actually are when booting, basically restoring the initial configuration I had set up when I installed Debian.

I am using LightDM as I remember choosing it when I installed Debian, so I will try to change the .conf files you mention to see if I can solve this issue. It's just really bothersome because it takes longer for the computer to boot because I have to wait for the computer to place the monitors in their correct position before I can do anything, basically freezing on the screen that I pictured earlier.

I will add another note if any of those files work, thank you!

[cephalopod_spider]

I understand now what the inxi -Gaz command is telling me, and it seems that the monitor positions are accurate, as the smaller monitor is on the left and the larger one is on the right, so I think that there must be something specifically on the configuration of the login area that swaps the displays from left to right when the computer boots. I will try to look into it, but I am very inexperienced with Linux so it will surely be very difficult.

I will mark this thread as solved, because I believe my question is not very precise and it's leaving room for ambiguity. After I find out more about this specific issue that is haunting my login screen, I will post a more focused question thread. Thanks to @mrmazda and [mention}FreewheelinFrank[/mention] for all the help.