I just installed the new Ubuntu 17.10 on my work notebook and found out a very common problem with the ACPI. The brightness controls (F5 & F6) are not working...

The solution to the problem is:

  1. Open the Terminal and type: sudo gedit /etc/default/grub
  2. Append acpi_osi=Linux to the GRUB_CMDLINE_LINUX item
  3. In the Terminal execute the following command: sudo update-grub
  4. Reboot your notebook

That's it! 👻