[SOLVED] Function key not working for brightness (f4 and f5) in Asus Vivobook in Ubuntu 18.04

I have solved the problem with fuction key for changing brightness in Asus Vivobook in Ubuntu. Just follow the steps:

1. Open Terminal (Ctrl+alt+T)

2. Paste following command

ls /sys/class/backlight/

Then you will get a result like:-

$ ls /sys/class/backlight/

intel_backlight

So, that means the brightness of your system is controlled by intel_backlight. So you have to update the grub with this directory. In case, if you see another directory and no intel directory is present, use the existing one in step 3.

3. Paste following command in terminal

sudo gedit /etc/default/grub 

Then grub file will be opened

Edit the following line 

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

to

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi=intel_backlight"

4. Save the file and close it.

5. Run the command

  sudo update-grub

6. Done. Now just restart your system and see the function keys are working.

Comment below if it is working for you!