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I have a Macbook2,1 with Ubuntu 12.04. When I start the computer the back light is on and I can see all of the boot stuff. Once the GUI begins to start up the backlight is turned completely off and I can not see anything. I do however hear the little ubuntu drum beat, can then type my password and log on. Once I have done this I can then use the brightness buttons to turn the brightness back up but the logon screen is always just blackness.

I can control the brightness from the command line using

 echo 500 | sudo tee /sys/class/backlight/intel_video/brightness

and I put this line into /etc/rc.local before the exit 0 but this doesnt do anything. How can I get the brightness back up when the GUI starts up?

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Since rc.local is run under UID 0, you could simplify the command to echo 500 >/sys/class/backlight/intel_video/brightness Why not follow it with cp /sys/class/backlight/intel_video/brightness /tmp/brightness so you can see if it took the 500? –  waltinator May 17 at 21:13
    
Do you have any other displays plugged into your MacBook? Just eliminating the obvious... –  Benjamin R May 17 at 21:30
    
Tried @waltinator suggestion. 500 is copied to /tmp/brightness but still dark login screen. So I guess its being adjusted after rc.local is run? And, no, nothing plugged in but the power cable. –  Robmotron May 24 at 20:36

2 Answers 2

Still not exactly sure how to change this setting but the last round of updates from the update manager seems to have fixed this. Will post if I can find which update did this or what setting to change.

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The following worked for me:

  1. Find your ACPI interface: grep acpi_video /var/log/Xorg.0.log
  2. Get the desired brightness level: set brightness to desired level then run cat /sys/class/backlight/acpi_videoX/brightness, substituting X for the ACPI number found on step 1
  3. Create a fixbrightness.conf file: run gksu gedit /etc/init/fixbrightness.conf and paste the following, replacing BRIGHTNESS_VALUE with the number gotten from the previous step and X for your ACPI interface number:

    description "Sets brightness after graphics device is loaded"
    
    start on graphics-device-added`
    task
    exec /bin/echo BRIGHTNESS_VALUE > /sys/class/backlight/acpi_videoX/brightness
    
  4. Save and reboot.

Source: http://www.webupd8.org/2014/10/fix-brightness-getting-reset-to-very.html

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