I have two displays. I can successfully set brightness for the first display using e.g. xbacklight -set 30, but I cannot dim my second display connected to HDMI. I tried xbacklight -display HDMI1 -set 30, and xbacklight -display 1 -set 30, but I've got RANDR Query Version returned error -1 in both cases.

What do I have to write as the -display parameter?


xrandr --listmonitors
Monitors: 1
 0: +*HDMI1 1920/527x1080/296+0+0  HDMI1

The following command works perfectly:

xrandr --output HDMI1 --brightness 0.3
  • I have the same problem. Did you ever solve this? – Leo Aug 29 '19 at 21:34
  • About your P.S.: backlight and brightness are not the same thing. See unix.stackexchange.com/a/421308/270277 – prosoitos Jan 17 at 16:54
  • I just answered the same question here – prosoitos Jan 17 at 18:58
  • That's not really an answer to this question but an alternative way. – André Yuhai Sep 6 at 7:50

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