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I'm in the process of moving from a machine running 20.04 (windowing system X11) to a new one running 22.04 (windowing system Wayland), and I have not been able to find a functional method for adjusting monitor brightness from the command line.

I have tried the following on the new machine:

  • Running xrandr --output MONITOR_NAME --brightness 0.5 (on my new machine MONITOR_NAME is XWAYLAND0 or similar, while on the old it was HDMI-1): the command appears to run without error, but the brightness does not change.
  • Changing the windowing system from Wayland back to X11 (as suggested by this post): this seemed to cause unrecoverable screen freezes, and I had to force several reboots before I was able to put it back to Wayland.
  • Using wlr-randr: I get an error that says compositor doesn't support wlr-output-management-unstable-v1, and further investigation indeed suggests gnome doesn't support wlr-randr

Has anyone come up with a functional method for changing brightness from the command line in 22.04 with Wayland as the windowing system?

(My end goal here is to be able to run an alias dim in the terminal and have it dim my external monitor to a pre-selected level, which worked very nicely on my old laptop but doesn't seem possible now.)

Edit: The solutions suggested in this question also don't seem to work so far, since I'm specifically hoping to adjust brightness on an external monitor.

  • gammastep throws the error Error: Failed to start adjustment method: wayland (and doesn't seem like an optimized tool for brightness-specific changes in the first place)
  • As noted in the other question, brightnessctl and light don't recognize external monitors - it looks like there might be an option to fiddle around with a kernel module and get brightnessctl to work, so I'm going to try that next, but I'd still prefer a solution that doesn't require that.
  • As noted above, wlr-randr isn't supported by gnome
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I don't know if you already found something that works for you, but what I found and worked for me was the ddcutil cli to directly send the commands to the monitor: https://moverest.xyz/blog/control-display-with-ddc-ci/

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