I've just bought a new laptop and I tried to create Keyboard Shortcut to manage screen backlight because the keyboard has them (on the key) but my Xubuntu 16.04 doesn't recognize the correct action.

I've opened the Keyboard Manager, I add a new command, but when I push the combination (Fn+F5 or Fn+F6) it doesn't "feel" it, like if I haven't pushed anything at all.

On the other hand, combinations like Fn+F3 or Fn+F4 are working, also if there isn't any second action printed on the keyboard (see picture).

laptop keyboard

Keyboard settings manager xubuntu

So is it possible to "activate" all the keys?

  • What laptop model do you have? Does anything appear in the system logs when you press one of the unrecognized keys? Depending on the laptop (and occasionally on the BIOS configuration), some keys may send ACPI events rather than keyboard events. – Gilles Jun 3 '17 at 23:02
  • @Gilles it's an AsusPro, where can I see logs or check ACPI events? Many thanks – xdola Jun 3 '17 at 23:09

The Fn keyboard combinations work differently on every laptop.

Brief overview: When you press these combinations, some laptops produce keyboard events, some laptop produce ACPI events. The Linux kernel interprets these, and makes them available on a /dev/input/event* device. X reads those and converts them into X keyboard events. An application, typically the window manager, reacts to them and tries to change backlight intensity.


(1) Run evtest as root, select your keyboard, see if you get backlight key events.

(2) Run xev, see if you get X backlight key events.

(3) Run acpi_listen to see if you get ACPI events.

(4) Try to control your backlight brightness by writing numbers as root into /sys/class/backlight/<backlight>/brightness.

What you have to change to make it work depends on which part fails.

  • Thanks for the answer. But what if none of your method (1, 2, 3) is able to see button pressed? The thing that I don't understand is: if it is able to feel Fn+F3 why Fn+F5 isn't a combination / key for it? – xdola Jun 4 '17 at 23:02
  • If you can't see it with (1) or (3), it's going to be difficult - next step is digging through the ACPI tables, which requires a fair bit of technical expertise, more than I can explain here. Fn is non-standard, and all keys are handled differently - some combinations generate normal key events, some don't. Blame the Laptop makers for making things difficult, and not documenting them. – dirkt Jun 5 '17 at 4:03

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