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I have screen energy saving enabled, but my monitors never turn off automatically - even when the screen is locked. I can -briefly- manually turn them off using xset dpms force off, but in a couple of seconds both of my monitors turn on again, without any interaction from me.

Is there a way to find out why this keeps happening? Can a running application do this, and if so, how would I identify the culprit?

OS is Debian 10 64-bit with KDE 5.

jaymmer - Reinstate Monica
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  • Does `dmesg` hint at anything? – pfnuesel Aug 26 '21 at 12:58
  • Some mice can generate movement events while laying on an even surface. Disconnect your mouse and check if it helps. Also, some applications can disable monitor power saving, e.g. video players like `mpv`. – Artem S. Tashkinov Aug 26 '21 at 13:04
  • I've tried unplugging the mouse, and even unplugging the keyboard (immediately after `sleep 5 && xset dpms force off`), neither of which worked. `dmesg` output appears to contain nothing of relevance, neither do `~/.xsession-errors` or `/var/log/Xorg.0.log`. I can't think of anywhere else to check. – jaymmer - Reinstate Monica Aug 26 '21 at 23:28
  • I had a similar problem in Ubuntu 2204 Gnome, on a 2021 model Asus laptop plugged into a Dell monitor. Take a look at my answer or some of the other answers on this thread: https://unix.stackexchange.com/a/704934/405507 – Vijay Prema Jun 03 '22 at 23:20

2 Answers2

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Of course the solution presents itself within a day of asking the question. While trying to fix an unrelated problem that someone has ran into before, I stopped the kscreen_backend_launcher process (using kill -STOP), and not only do my monitors go to and stay asleep properly, my desktop stops rearranging itself every time I turn my HDMI monitor off.

I don't know why that process wants to keep my monitors awake, but at least I now have a workaround.

jaymmer - Reinstate Monica
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I dealt with this problem and it turned out that my monitor was set to "auto" for source. and each time the monitor was powered off via dpms, when it cycled for a new source it turned the monitor back on. I set the source from auto to the dedicated source (HDMI) and the problem was solved.

Harold Callahan
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