Hi I have just installed Elementary OS Loki 0.4.1, on to my acer aspire 5742 PEW71 laptop. I have it dual booted with windows 7 which can alter screen brightness, however when i change the brightness in windows 7 it does not alter Element OS. It has received all the latest updates and have tried the following:

  1. xbacklight
  2. cd /sys/class/backlight/*/ 
    sudo chmod 777 ./brightness 
    sudo echo $(cat max_brightness) > ./brightness``
  • Please include relevant hardware information like computer/laptop, which brand which version etc. Dec 25, 2017 at 0:35
  • Hi peter, i have included the laptop model, is there any other information that i can add, that may be of use Dec 25, 2017 at 12:38
  • I would try searching on something like "Acer Aspire brightness ubuntu". (Ubuntu because ElementaryOS is build on it and it's a very common Linux distro) It might be a driver issue. See for example: ubuntuforums.org/showthread.php?t=2200860 Dec 27, 2017 at 21:48

1 Answer 1


Originally posted by divergex:

Here is the solution that worked on my Aspire 5740; In the terminal, run:

sudo gedit /etc/default/grub

when the file opens, look for the line similar to:


and add acpi_osi= to the list, so it looks like:

GRUB_CMDLINE_LINUX_DEFAULT="quite splash acpi_osi="

save the file, then exit gedit. Next, be sure to run:

sudo update-grub

to make the changes permanent. Exit the terminal and reboot.

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