Udev rule not running

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1

I have a script that I want to run when I add a monitor. The script, monitor-rescale has the following contents:


xrandr=$(xrandr)

con_monitors=$(xrandr | grep -c " connected ")

if [[ $con_monitors -gt 1 ]]; then
    gsettings set org.gnome.desktop.interface text-scaling-factor 2
    gsettings --schemadir ~/.local/share/gnome-shell/extensions/dash-to-dock@micxgx.gmail.com/schemas/ set org.gnome.shell.extensions.dash-to-dock dash-max-icon-size 74

fi

if [[ $con_monitors -eq 1 ]]; then
     gsettings set org.gnome.desktop.interface text-scaling-factor 1.4
     gsettings --schemadir ~/.local/share/gnome-shell/extensions/dash-to-dock@micxgx.gmail.com/schemas/ set org.gnome.shell.extensions.dash-to-dock dash-max-icon-size 43

 fi

It has the necessary permissions. More specifically -rwxr-xr-x. 1 spurz spurz 637 Nov 6 17:59 monitor-scale.

I have created a udev rule in the following file /etc/udev/rules.d/99-monitor-hotplug.rules and the contents of that file are:

SUBSYSTEM=="drm", ACTION=="change", RUN+="/home/spurz/Documents/configs/monitor-scale"

I have run sudo udevadm control --reload after adding the udev rule but nothing happens when I unplug the monitor still.

The command udevadm monitor does register a monitor addition when I add the monitor(or when I remove it).
Some of the output when I add is:

KERNEL[87678.851509] add      /devices/pci0000:00/0000:00:14.0/usb1/1-1 (usb)
KERNEL[87678.871688] add      /devices/pci0000:00/0000:00:14.0/usb1/1-1/1-1:2.0 (usb)
KERNEL[87678.871723] bind     /devices/pci0000:00/0000:00:14.0/usb1/1-1 (usb)
UDEV  [87678.874081] add      /devices/pci0000:00/0000:00:14.0/usb1/1-1 (usb)
UDEV  [87678.875158] add      /devices/pci0000:00/0000:00:14.0/usb1/1-1/1-1:2.0 (usb)
UDEV  [87678.876260] bind     /devices/pci0000:00/0000:00:14.0/usb1/1-1 (usb)
KERNEL[87679.003750] change   /devices/platform/USBC000:00/typec/port0 (typec)
KERNEL[87679.003775] add      /devices/platform/USBC000:00/typec/port0/port0-partner (typec)
KERNEL[87679.003922] change   /devices/platform/USBC000:00/power_supply/ucsi-source-psy-USBC000:001 (power_supply)
UDEV  [87679.004754] change   /devices/platform/USBC000:00/typec/port0 (typec)
UDEV  [87679.005514] change   /devices/platform/USBC000:00/power_supply/ucsi-source-psy-USBC000:001 (power_supply)
UDEV  [87679.005772] add      /devices/platform/USBC000:00/typec/port0/port0-partner (typec)
KERNEL[87679.841696] change   /devices/platform/USBC000:00/power_supply/ucsi-source-psy-USBC000:001 (power_supply)
UDEV  [87679.842789] change   /devices/platform/USBC000:00/power_supply/ucsi-source-psy-USBC000:001 (power_supply)
KERNEL[87680.054427] add      /devices/platform/USBC000:00/typec/port0/port0-partner/port0-partner.0 (typec)
KERNEL[87680.054451] bind     /devices/platform/USBC000:00/typec/port0/port0-partner/port0-partner.0 (typec)
UDEV  [87680.055271] add      /devices/platform/USBC000:00/typec/port0/port0-partner/port0-partner.0 (typec)
UDEV  [87680.055801] bind     /devices/platform/USBC000:00/typec/port0/port0-partner/port0-partner.0 (typec)
KERNEL[87680.288944] change   /devices/platform/USBC000:00/typec/port0/port0-partner (typec)
UDEV  [87680.289588] change   /devices/platform/USBC000:00/typec/port0/port0-partner (typec)
KERNEL[87680.452997] change   /devices/pci0000:00/0000:00:02.0/drm/card1 (drm)
UDEV  [87680.460055] change   /devices/pci0000:00/0000:00:02.0/drm/card1 (drm)
KERNEL[87680.461434] change   /devices/platform/USBC000:00/typec/port0/port0-partner/port0-partner.0 (typec)
KERNEL[87680.461451] add      /devices/virtual/usb_power_delivery/pd1 (usb_power_delivery)
UDEV  [87680.462228] change   /devices/platform/USBC000:00/typec/port0/port0-partner/port0-partner.0 (typec)
UDEV  [87680.462275] add      /devices/virtual/usb_power_delivery/pd1 (usb_power_delivery)
KERNEL[87681.455470] change   /devices/platform/USBC000:00/power_supply/ucsi-source-psy-USBC000:001 (power_supply)
KERNEL[87681.455512] change   /devices/platform/USBC000:00/typec/port0/port0-partner (typec)
UDEV  [87681.455962] change   /devices/platform/USBC000:00/power_supply/ucsi-source-psy-USBC000:001 (power_supply)

Is there something wrong with my udev rule?

2

I’m not sure about the udev rule, but it looks like it should work.

The script, however, has some problems. First, it has no shebang (#!/bin/bash), so the kernel doesn’t know how to execute it. More significantly, udev is going to run it as root and outside your session.

Also, I don’t think this line is doing anything useful:

xrandr=$(xrandr)

I’d make a systemd user service and start that from the udev rule:

RUN+="/usr/bin/systemctl --user -M spurz@ start monitor-scale.service"

[Unit]
Description=Monitor scale adjustment

[Service]
Type=oneshot
ExecStart=/home/spurz/Documents/configs/monitor-scale

Save that as ~/.config/systemd/user/monitor-scale.service

3

If you are running Xort ant not Wayland you create the file /etc/X11/xorg.conf.d/50-mode-1280x720.conf

# Set default screen resolution.

Section "Screen"
    Identifier    "Default Screen"
    SubSection    "Display"
        Modes    "1280x720"
    EndSubSection
EndSection

You can also try to add video=1280x720 to the kernel command line, but seems to be mostly ignored in graphical environment.

Otherwise Gnome and other desktop environment has settings for this.