GDM does not respect my monitors.xml file

zu0107 · 2025-09-24 06:47:18

My primary display is currently in portrait mode, so I need to rotate the display 90 degrees to the left.
According to the ArchWiki, I should be able to copy my existing monitor.xml file:

Some desktop environments store display settings in ~/.config/monitors.xml. xrandr commands are then generated on the base of the file content. GDM has a similar file stored in /var/lib/gdm/.config/monitors.xml.
If you have your monitors setup as you like (resolution, refresh rate, orientation, scaling, primary and so on) in ~/.config/monitors.xml and want GDM to honor those settings:
# cp /home/user/.config/monitors.xml /var/lib/gdm/.config/

I've followed the direction, but I still see that the screen remains in the landscape mode, unlike what my monitors.xml file is configured to.

I've confirmed that:

the monitors.xml file works fine on my GNOME desktop
GNOME is running under Wayland, and the monitors.xml is based on Wayland GNOME

Is there anything I am missing here?

alex1124 · 2025-09-24 10:02:04

This seems to be due to the gdm user not being automatically created during the gdm installation, causing GDM to lack permissions to read the /var/lib/gdm directory. The issue appears to be in /usr/lib/sysusers.d/gdm.conf, you should check if this content is present:

 g gdm 120 -

This indicates that only the gdm user group was created, but not the gdm user.
In theory, you can manually create the gdm user and set its user directory to /var/lib/gdm to solve the problem, but I have not been successful.

zu0107 · 2025-09-25 13:02:02

I've added my own entry to /etc/sysusers.d/gdm.conf with the following content to create a gdm user, but the problem still persists.

u! gdm 120 - /var/lib/gdm

I even made the /var/lib/gdm directory owned by the newly-created gdm user but the problem still persists. Not sure where to go from here.

seth · 2025-09-25 14:13:33

ls -ld /var /var/lib /var/lib/gdm /var/lib/gdm /var/lib/gdm/.config /var/lib/gdm/.config/monitors.xml

pampar · 2025-09-26 21:01:20

Hi! I came over from a different thread I created about a similar issue, I won't go into the details about my current setup here again.

Continuing that thread

I set global execution perms on /var/lib/gdm/.config and verified that gdm-greeter had read perms on monitors.xml by running

sudo -u gdm-greeter cat /var/lib/gdm/.config/monitors.xml

Rebooted, the config still wasn't applied.

seth wrote:

For clarification: you've been running on X11 before so this might have been some X11 server config as well?

Honestly I'm not sure. As I said in the original thread, this config works on user sessions that say they are wayland, however, it only worked on the login screen when I disabled wayland for gdm in /etc/gdm/custom.conf (back on gnome 48) so it's confusing.
Here's a sample if it helps:

<monitors version="2">
  <configuration>
    <layoutmode>physical</layoutmode>
    <logicalmonitor>
      <x>0</x>
      <y>0</y>
      <scale>1</scale>
      <monitor>
        <monitorspec>
          <connector>HDMI-2</connector>
          <vendor>GSM</vendor>
          <product>LG TV</product>
          <serial>0x01010101</serial>
        </monitorspec>
        <mode>
          <width>3840</width>
          <height>2160</height>
          <rate>60.000</rate>
        </mode>
      </monitor>
    </logicalmonitor>
    <logicalmonitor>
      <x>0</x>
      <y>2160</y>
      <scale>1</scale>
      <primary>yes</primary>
      <monitor>
        <monitorspec>
          <connector>HDMI-1</connector>
          <vendor>GSM</vendor>
          <product>LG IPS FULLHD</product>
          <serial>0x01010101</serial>
        </monitorspec>
        <mode>
          <width>1920</width>
          <height>1080</height>
          <rate>60.000</rate>
        </mode>
      </monitor>
    </logicalmonitor>
  </configuration>
  [...]
</monitors>

Some other findings

I checked the env of the greeter's session process (/usr/lib/gdm-wayland-session) as root (formatted and truncated the output a bit):

$ cat /proc/7678/environ
HOME=/run/gdm/home/gdm-greeter
PATH=/usr/local/bin:/usr/bin
USER=gdm-greeter
XDG_RUNTIME_DIR=/run/user/60579
DCONF_PROFILE=gdm
GDM_SEAT_ID=seat0
GDM_SUPPORTED_SESSION_TYPES=wayland:x11
GDM_VERSION=49.0.1
GIO_USE_VFS=local
GNOME_SHELL_SESSION_MODE=gdm
PWD=/run/gdm/home/gdm-greeter
RUNNING_UNDER_GDM=true
SHELL=/usr/bin/nologin
USERNAME=gdm-greeter
XDG_CONFIG_HOME=/var/lib/gdm/seat0/config
XDG_CURRENT_DESKTOP=GNOME-Greeter:GNOME
XDG_DATA_DIRS=/usr/share/gdm/greeter:/usr/share:/usr/local/share/:/usr/share/
XDG_MENU_PREFIX=gnome-
XDG_SESSION_CLASS=greeter
XDG_SESSION_TYPE=wayland
XDG_STATE_HOME=/var/lib/gdm/seat0/state

Checked the $HOME dir, there was a .config directory, but no monitors.xml in it.
Checked $XDG_CONFIG_HOME, the correct monitors.xml was there with perms:
-rw-r--r-- 1 gdm-greeter nobody
verified with sudo that gdm-greeter can read it.

For reference here is the env for the same process of a logged in user session (also formatted, truncated):

XDG_SEAT=seat0
LOGNAME=pampar
USER=pampar
USERNAME=pampar
HOME=/home/pampar
PWD=/home/pampar
SHELL=/bin/bash
PATH=/usr/local/bin:/usr/local/sbin:/usr/bin
XDG_SESSION_TYPE=wayland
XDG_VTNR=2
XDG_SESSION_ID=9
XDG_SESSION_CLASS=user
XDG_RUNTIME_DIR=/run/user/1000
DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/1000/bus
MOTD_SHOWN=pam
XDG_CURRENT_DESKTOP=GNOME
GDMSESSION=gnome
DESKTOP_SESSION=gnome
XDG_SESSION_DESKTOP=gnome

seth · 2025-09-27 14:09:42

XDG_CONFIG_HOME=/var/lib/gdm/seat0/config

Do you have more luck w/ /var/lib/gdm/seat0/config/monitors.xml then?

pampar · 2025-09-27 14:19:10

No, it is there, but it doesn't get applied I guess.

Is it possible, that mutter, or xorg-xwayland does some sort of "translation" that makes it so my user session is actually x on wayland and that's why the config works, while the greeter is on normal wayland without this translation and that's why it doesn't get applied?
Do you have an idea how I could check that?

Thanks!

kk75 · 2025-09-27 17:22:38

seth wrote:

XDG_CONFIG_HOME=/var/lib/gdm/seat0/config
Do you have more luck w/ /var/lib/gdm/seat0/config/monitors.xml then?

For me it worked.

# cp /home/user/.config/monitors.xml /var/lib/gdm/seat0/config/
# chown gdm:gdm /var/lib/gdm/seat0/config/monitors.xml

Now I have my login in the right monitor with correct resolution in Gnome 49 under Wayland.
Thank you.

Last edited by kk75 (2025-09-27 17:32:16)

pampar · 2025-09-27 17:55:48

Also tried it, for me it still doesn't work sadly.

# set perms
chown :gdm /var/lib/gdm/seat0/config
chmod g+x /var/lib/gdm/seat0/config
# verify
sudo -u gdm cat /var/lib/gdm/seat0/config/monitors.xml
# Logged out of user, on lock screen it's still wrong

Afterwards I logged back in to set the perms back, but i found that /var/lib/gdm/seat0/config/ had it's perms reset already to drwx------, the owner userid changed from 60578 to 60579 and the gdm group was changed back to nobody.
I believe this is because gnome 49 uses systemd dynamic users for the greeter:
https://blogs.gnome.org/adrianvovk/2025 … endencies/
https://linuxiac.com/gnome-49-will-requ … tegration/

seth · 2025-09-28 07:25:18

The dynamic UID should™ not systematically lead to an inaccessible /var/lib/gdm/*/* ?
Have you tried to own /var/lib/gdm/seat0/config/monitors.xml to the GDM user/group?

pampar · 2025-09-28 12:16:59

Tried it right now, as soon as the greeter comes on, the owner gets reset to gdm-greeter:nobody. (I'm using an ssh session from a different computer to check this.)
Running id on gdm-greeter I see that it's group is gdm, so I'd think that instead of nobody, this automatic chown should set the owner group to gdm as well? Altough that wouldn't help with /var/lib/gdm/seat0/config getting it's perms reset to drwx------ automatically...
Can someone with a working gnome 49 install confirm for me what the owners should be on /var/lib/gdm/seat0/config/* please?
For me:

$ ls -ld /var/lib/gdm/ /var/lib/gdm/seat0/ /var/lib/gdm/seat0/config/ /var/lib/gdm/seat0/config/*
drwxr-xr-x 1 root        root    230 Sep 24 18:40 /var/lib/gdm/
drwxr-xr-x 1 root        root     22 Sep 24 18:40 /var/lib/gdm/seat0/
drwx------ 1 gdm-greeter nobody  196 Sep 24 18:40 /var/lib/gdm/seat0/config/
drwxr-xr-x 1 gdm-greeter nobody    8 Sep 24 18:40 /var/lib/gdm/seat0/config/dconf
drwxr-xr-x 1 gdm-greeter nobody   26 Sep 24 18:40 /var/lib/gdm/seat0/config/gnome-session
drwxr-xr-x 1 gdm-greeter nobody    6 Sep 24 18:40 /var/lib/gdm/seat0/config/ibus
-rw-r--r-- 1 gdm-greeter nobody 6132 Sep 22 01:03 /var/lib/gdm/seat0/config/monitors.xml
drwxr-xr-x 1 gdm-greeter nobody   12 Sep 24 18:40 /var/lib/gdm/seat0/config/pulse
-rw------- 1 gdm-greeter nobody  633 Feb  5  2025 /var/lib/gdm/seat0/config/user-dirs.dirs
-rw-r--r-- 1 gdm-greeter nobody    1 Feb  5  2025 /var/lib/gdm/seat0/config/user-dirs.locale

Last edited by pampar (2025-09-28 12:19:12)

kk75 · 2025-09-28 15:45:08

This is my result:

# ls -ld /var/lib/gdm/ /var/lib/gdm/seat0/ /var/lib/gdm/seat0/config/ /var/lib/gdm/seat0/config/*
drwxr-xr-x 15 root  root   4096 Sep 23 22:53 /var/lib/gdm/
drwxr-xr-x  4 root  root   4096 Sep 23 22:53 /var/lib/gdm/seat0/
drwx------  6 60578 nobody 4096 Sep 23 23:33 /var/lib/gdm/seat0/config/
drwxr-xr-x  2 60578 nobody 4096 Sep 23 22:53 /var/lib/gdm/seat0/config/dconf
drwxr-xr-x  3 60578 nobody 4096 Sep 23 22:53 /var/lib/gdm/seat0/config/gnome-session
drwxr-xr-x  3 60578 nobody 4096 Sep 23 22:53 /var/lib/gdm/seat0/config/ibus
-rw-r--r--  1 60578 nobody 1027 Sep 27 18:44 /var/lib/gdm/seat0/config/monitors.xml
-rw-r--r--  1 60578 nobody  989 Dec 17  2023 /var/lib/gdm/seat0/config/monitors.xml~
drwx------  2 60578 gdm    4096 Sep 23 23:33 /var/lib/gdm/seat0/config/pulse
-rw-------  1 60578 nobody  633 Apr 30  2023 /var/lib/gdm/seat0/config/user-dirs.dirs
-rw-r--r--  1 60578 nobody    5 Apr 30  2023 /var/lib/gdm/seat0/config/user-dirs.locale

When I copied my /home/user/.config/monitors.xml to /var/lib/gdm/seat0/config/, I changed owner to gdm:gdm.
After a reboot it was automatically changed to 60578:nobody, but it works.

cbrnr · 2025-10-06 09:20:57

I think the old mechanism of copying a custom monitors.xml to /var/lib/gdm/.config/ does not work anymore with GNOME 49, because they removed the static gdm user (https://gitlab.archlinux.org/archlinux/ … 58f577140c). However, I have no idea how to use a custom monitor configuration now. It doesn't make sense to me to still put the config into /var/lib/gdm, so I'm hoping that there is a new recommended way to do that.

Last edited by cbrnr (2025-10-06 09:22:13)

seth · 2025-10-06 12:54:37

https://gitlab.gnome.org/GNOME/gdm/-/is … te_2456888

Arch Linux

#1 2025-09-24 06:47:18