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[Bug 1545266] Re: screen brightness slider has no effect


The steps outlined in the official documentation are working fine - I
have set up the two monitors, and both are usable in many ways.  But I
can not find a way to use software to adjust the brightness of them.

I had another computer which was a laptop, and it worked to use f.lux on
the external monitor but not on the integrated monitor, under Trusty
14.04, so I would like it to work on this computer too, with the two
integrated monitors.

I am linking another thread, where I had a bug report that I could not
figure out how to edit, that I changed into a Question, so I have three
IDs for this problem now.  The question version seems somewhat useful.
I marked the bug version of that one invalid.  I think it may be best if
I merge all the information into this report.

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  screen brightness slider has no effect

Status in ubuntu-docs package in Ubuntu:

Bug description:
  Trusty Tahr 14.04 LTS, seems to be fully updated

  f.lux also has no effect.

  Also when i try to do
   sudo echo 50 > /sys/class/backlight/acpi_video0/brightness
  then it says 'bash: brightness: permission denied'.
  (From this page: http://pastebin.com/HzzHrS2g).

  product: OptiPlex 7010 (OptiPlex 7010)

            description: CPU
            product: Intel(R) Core(TM) i3-3240 CPU @ 3.40GHz
            description: Host bridge
            product: Xeon E3-1200 v2/3rd Gen Core processor DRAM Controller
            vendor: Intel Corporation
               description: VGA compatible controller
               product: Xeon E3-1200 v2/3rd Gen Core processor Graphics Controller

  I would love to help provide some more help on my dual monitor setup.
  I found this documentation: https://wiki.ubuntu.com/X/Config/Resolution
  It says I should run $gnome-display-properties. Seems to be out of date. 
  gnome-display-properties: command not found

  I guess it would be annoying to say it's a security vulnerability
  although if my screen isn't dim someone could more easily look through
  the window and see what I am typing on the screen.

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