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Here is what it looks like when I go to the "change brightness" option. I am booting in recovery mode because when I boot to normal Ubuntu mode there is nothing you can see on the screen, I can only hear the login sound.

So I thought I would need to change the brightness but neither Fn + F6 works, nor do I get an option to change the brightness in the settings.

Screenshot

S.L. Barth is on codidact.com
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personinsack
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  • Perhaps my answer here may be a useful workaround. As for the normal mode, I'd suggest you install different greeter - like lightdm-gtk-greeter – Sergiy Kolodyazhnyy Mar 10 '15 at 14:43
  • got this after enter this in terminal bash: /sys/class/backlight/acpi_video0/brightness /sys/class/backlight/acpi_video0/brightness: No such file or directory – personinsack Mar 10 '15 at 14:48
  • what does this say: ls /sys/class/backlight/ – Sergiy Kolodyazhnyy Mar 10 '15 at 14:50
  • it does nothing when i enter ls /sys/class/backlight/ – personinsack Mar 10 '15 at 15:09
  • Did you verify that your Fn+... keys work? That they weren't hijacked or shadowed? – LAFK says Reinstate Monica Mar 10 '15 at 15:36
  • Your question may boil down to same case as in "Dell Chromebook 11 - unable to set backlight and /sys/class/backlight/ folder is empty" or in "/sys/class/baclight folder is empty, leading to blank screen". Former has an answer that I partially quoted. You may want to pick it up with answer's author - he might know more. – LAFK says Reinstate Monica Mar 10 '15 at 16:08
  • well then then is nothings there i can do then cause ubuntu thinks i have a crt but i have to have some brightness cause the screen is really blank on normal ubuntu mode i have to boot it up in recovery also when i hibernate in recovery it kinda opens up in normal ubuntu mode – personinsack Mar 11 '15 at 06:01
  • got my brightness back http://i.imgur.com/nT0Oaae.png. i booted up in the third option of the advanced settings and i somehow have my brightness back yesss!!!! – personinsack Mar 11 '15 at 06:17

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Manual way

Works for some systems, though not yours, apparently, since ls /sys/class/backlight/ shows nothing for you. Sometimes instead of intel_backlight you'll have acpi_video0, or something else.

You can manually change the brighntess level all the way down (to disable it altogether) by doing echo 23 > /sys/class/backlight/intel_backlight/brightness as a root. "23" is the desired brightness level. If you put "0", the screen will look blank.

From Adam Ryczkowski's comment here, which helped my friend in similar case.

Empty /sys/class/backlight/ means unrecognized hardware

When I noticed your exchange with @Serg, I thought "why would that folder be empty" and search showed this:

If /sys/class/backlight/ is empty, that means that the kernel thinks you have a big bad old CRT attached to the system and that you have to turn the big fat knobs named "Brightness" and "Contrast" on the from to change... well, brightness and contrast...

source: @Fabby's answer to another AskUbuntu question.

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