Function Keys Do Not work (Brightness & Sound) Ubuntu 16.04

1. Edit GRUB config file to pass a kernel boot parameter

   • Open Terminal
   • type sudo -H gedit /etc/default/grub
   • Find this line: GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
   • Add acpi_osi= immediately following quiet splash to give: GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi="
   • The next line should look like this: GRUB_CMDLINE_LINUX=""
   • SAVE and CLOSE file
   • In terminal, type sudo update-grub

2. Create .CONF file

   • Open Terminal
   • type (or copy/paste): sudo -H gedit /usr/share/X11/xorg.conf.d/20-intel.conf

   • Enter this in the file line for line:

     Section "Device"
     Identifier  "card0"
     Driver      "intel"
     Option      "Backlight"  "intel_backlight"
     BusID       "PCI:0:2:0"
     EndSection
     

   • SAVE and CLOSE file

3. Reboot computer

The above steps fixed my problem and I was able to use the function keys to control brightness and volume on my machine. I tried several things and edited the GRUB file several times, updating and rebooting every time. Some threads suggested edited the BIOS, others suggested installing xbacklight. It took a while to troubleshoot. If my solution doesn't work for you, here are threads that helped me:

• This one edits GRUB slightly differently
• This is what I used the create the 20-intel.conf file (but the GRUB specifics did not work for me)
• Why does the Kernel Boot Parameter Set ACPI OSI Linux
• Linux Kernel Boot Parameters

You might have the FnLock activated. You might be able to deactivate it by pressing Fn + Esc. Source

Please check this article. You might need to change the fnmode value in sys/module/hid_apple/parameters/fnmode. For me it worked by changing it from 1 to 0. I did not need to reboot or anything.