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I'm running Ubuntu Gnome 14.04 on a Thinkpad X1 Carbon. When I unplug the HDMI cable, my brightness comes down to zero, and I can't increase it again.
With Fn + F9 as I normally would.

storm
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Costa Michailidis
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1 Answers1

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I faced the same problem before on my laptop Lenovo z500 ideapad after searching i found this solution :

 1. open terminal 
 2. sudo gedit "/etc/default/grub"
 3. append "acpi_backlight=vendor" to GRUB_CMDLINE_LINUX_DEFAULT
 4. GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"
 5. save and close gedit
 6. sudo update-grub
 7. restart

If nothing changes , you can check the solutions of this question.

Mohamed Slama
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  • Hahaa, no I can't adjust brightness at all. I'm gonna try to revert back. – Costa Michailidis Jun 29 '16 at 16:18
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    for advice if not working for all answers in the attached url specially SPRBRN answer upgrade to 16.04 i have had the same issue on linux mint , but on ubuntu was working fine @Costa – Mohamed Slama Jun 29 '16 at 19:20