keyboard backlight is not working after update

Issues related to applications and software problems
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datthu
Posts: 1
Joined: 2018/12/07 16:40:17

keyboard backlight is not working after update

Post by datthu » 2018/12/07 16:47:48

My keyboard backlight is not working after software update . I tried different solutions and commands but didnt work .

I tried using commmands

# xset led on
# xset led 3
# xmodmap -e 'add mod3 = Scroll_Lock'

None of the above commands are working .
My laptop specs

Asus UX430UA intel i7 7th gen
Running Cent OS 7

Looking forward for a solution .
Thank You

lightman47
Posts: 831
Joined: 2014/05/21 20:16:00
Location: Central New York, USA

Re: keyboard backlight is not working after update

Post by lightman47 » 2018/12/07 18:36:51

I experienced exactly this after the 7.6 update with Gnome. Have you checked Settings/Power/keyboard brightness? Mine was set to zero. After setting it to mid-range and reboot, it was again set back to the low end. However, the next adjust and reboot and it worked!

Note: Prior to discovering the above settings I panicked and installed 'system-config-keyboard' and 'system-config-keyboard-base' so I am unable to tell you whether the setting is/isn't contained in those packages.

lightman47
Posts: 831
Joined: 2014/05/21 20:16:00
Location: Central New York, USA

Re: keyboard backlight is not working after update

Post by lightman47 » 2018/12/11 21:05:03

OK - this has now become a 'problem'.

It seems that my 'settings' don't survive daily shutdown/startups! I have to AGAIN edit the setting mentioned above after only a couple of days.

lightman47
Posts: 831
Joined: 2014/05/21 20:16:00
Location: Central New York, USA

Re: keyboard backlight is not working after update

Post by lightman47 » 2018/12/29 15:33:09

OK - I've been intermittently investigating and I found a one-byte file that controls this. It is /var/lib/systemd/backlight/platform-dell-laptop:leds:dell::kbd_backlight

The content of mine was "0". I noted also that it had been edited last at midnight last night (shutdown time). I then adjusted the backlight through the GUI interface in Settings, as I'd mentioned in a previous post. This turned on the backlight. I refreshed my cli directory listing to find that this file was still un-touched since the shutdown (hmm)! I then waited till the backlight went out and, as root, edited the file manually. I changed the"0" to a "5" and saved the file - the keyboard backlight came on immediately and stayed on for the proper duration.

As it was always unpredictable, I am just going to wait to see if my edit will survive a shutdown/boot. If not, I've already written a quick & dirty script to plug into my startup if needed.

EDIT:
Something in my 'solution' is in error!

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