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I'm running Ubuntu 10.10 on a Cr48. I'm attempting to bind xbacklight -dec 10 to f6 (decrease brightness in chrome os) and xbacklight -inc 10 to f7 (increase brightness in chrome os). The decrease command works fine, but the increase command appears to have no effect. It's the same whether I run the command from the command line or use the bindings I set in CompizConfig Settings Manager.

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For me, the smallest increase that works is 13. Decreases of any size dim the screen, although I cannot see any difference between -dec 1 and -dec 10

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For me it does not increment if the percentage provided is less than 10. +9 makes no effect. – mcmlxxxiii May 28 '15 at 4:20
For me the smallest increase that works is 15. – Xylol May 14 at 8:22

You can change the brightness by changing some setting files.

  1. Open a terminal

  2. Login as root. sudo su

  3. Type echo -n 100 > /proc/acpi/video/DVGA/LCD/brightness.

  4. If you get a "No such file or directory" error, replace DVGA with VGA.

  5. 100 is the highest brightness level (100%). For example, just change the 100 to 50, to dim your display by 50 percent.

I hope this helped you and I don't know if it's possible to fix this bug with xbacklight. If you really want to work with xbacklight, I'd create a bug report.

-- Daniel

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I have a /proc/acpi/video/OVGA/ folder, but no LCD folder or brightness file. – gregghz Apr 12 '11 at 17:29
@greggory.hz that's strange, seems like a driver problem – omnidan Apr 12 '11 at 18:13

I had this same issue at first... I think it's that the default is to take 20 steps to complete the transition... this combined with your small 10% change breaks things it seems.

I got mine to work by making my functions as such:

brightness up => xbacklight -steps 1 -inc 20 brightness down => xbacklight -steps 1 -dec 20

  • Also, I saw in the above answer about LCD vs OVGA. You won't get LCD becuase it's a notebook. They should be OVGA ... something like: /proc/acpi/video/OVGA/DD01/

But if you setup your steps to be 1 and increase your percent changes to 20 or more you should be just fine with xbacklight!

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