Ubuntu 16.04 with Lenovo Ideapad 500S 13 ISK keyboard backlight

Question

I'm using this configuration for about a year, but only recently realized that keyboard back light don't work (even with the windows 10 which is my dual-boot).
When the laptop changes it's state e.g. goes awake, turned on, the back light goes on, then fades away slowly, but that's it. No way to turn it on again with Fn + Space which is in the documentation. I got replaced the memory for a bigger one, and tweaked the wifi, because there were no driver for it.

I found some answers elsewhere which recommended to echo > '1' to some files deep in my /dev directory (to force the state of the backlight). This was base on this answer.

My exact command was:

echo 1 > /sys/class/backlight/intel_backlight/brightness

because haven't found anything similar in the answer mentioned above. It returned permission error even with sudo, so I gave up on that one.

None of them worked for me. Where should be the problem and how could I resolve it?

UPDATE

I checked those commands again by chmodding the files here to be writeable for root and it turned out these are related to the screen backlight (because putting 1 to the bl_brightness file here made my screen totally dark.

Answer 1

Here is the file for keyboard backlight, /sys/devices/platform/thinkpad_acpi/leds/tpacpi::kbd_backlight/brightness.

I used nano editor after chmoding it to change its values. There were 3 values (0,1,2) 2 being the brightest.

Tested for a Lenevo ThinkPad Yoga 460, on Ubuntu 18.04 LTS