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When I press brightness contrast button to reduce and increase the brightness in Ubuntu it is neither showing any brightness bar nor having any effect on brightness.

However, when I manually change my brightness, it is working.

Zanna
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Amit Aslia
  • 1
  • Unclear. Brightness issues are rather hardware-dependent. Please add your machine details , and explain what button you mean, and what you mean by "manually" – Zanna Jul 07 '17 at 21:53

1 Answers1

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The file you should fix is named "grub" at this address: Open Nautilus (Files), go to Computer

/etc/default/grub

to edit this you should have root access or just open terminal and run this

sudo -H gedit /etc/default/grub

Check this out: 

# If you change this file, run 'update-grub' afterwards to update
# /boot/grub/grub.cfg.
# For full documentation of the options in this file, see:
#   info -f grub -n 'Simple configuration'

GRUB_DEFAULT=0
GRUB_HIDDEN_TIMEOUT=0
GRUB_HIDDEN_TIMEOUT_QUIET=true
GRUB_TIMEOUT=10
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
GRUB_CMDLINE_LINUX=""

on the 11th line it says:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

so change it to

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"

and then run this command in terminal

sudo update-grub

then it should be fixed after restarting the system.

Sometimes it doesn't work like this, you may like to test the change like this:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
GRUB_CMDLINE_LINUX="acpi_backlight=vendor"

don't forget to run sudo update-grub and restart

Zanna
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Mirza
  • 351
  • /etc/default/grub is the actual location of the file, not Computer/etc/default/grub. – wjandrea Jun 30 '17 at 14:08
  • The part about how you may not be able to access the file is pointless. You don't need to run sudo gedit then use the "Open" dialog, but just give the absolute path of the file in the command: sudo gedit /etc/default/grub, as you wrote. – wjandrea Jun 30 '17 at 14:08
  • @wjandrea , you are right as a pro but lots of people using "Files" browser can't find it because "Files" opens "/home" as default. so they just need to click on the "computer" on the left side to find "/etc" at "/" – Mirza Jul 01 '17 at 07:53
  • Oh, I see what you're getting at, but that's a confusing way to explain it, even for newcomers. It might be better to say "Open Nautilus (Files), go to Computer ...", but given the scope of your answer, you don't even need to mention Nautilus. I would say just leave it out entirely, especially since not everyone uses Nautilus; in fact, if I open Computer in Nemo, it takes me to computer:///, which has a list of disks, not the FS root. – wjandrea Jul 01 '17 at 18:46
  • @wjandrea , tnx dude, I used your advice and I hope it had got better – Mirza Jul 07 '17 at 11:27