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i have ubuntu 12.04 and sony laptop, and i've installed nvidia driver. screen brightness changing (with keyboard fn keys) and keyboard backlight works in unity, but it doesn't in kde. when i issue the command:
echo 8 > /sys/class/backlight/acpi_video0/brightness
it changes brightness, but it doesn't anything when i press brightness functions keys, even displaying a bar.
and also when i enter:
echo 1 > /sys/devices/platform/sony-laptop/kbd_backlight
it turns on keyboard backlight but it is not turned on by default. the best practice is what happens in windows: turn it on when you're in a dark place, using a light sensor.

thanx for your help ;)

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You might want to look at this answer, starting from #4. – Oleh Prypin Aug 5 '12 at 13:03
it won't work since lsmod | grep ^i915 doesn't output anything. – sazary Aug 6 '12 at 0:19

Thanks a lot mate,this command :

echo 8 > /sys/class/backlight/acpi_video0/brightness

Helped me change brightness levels in Kubuntu, however in Ubuntu Fn keys work quite fine after adding Option Registry Dwords..... line in xorg.conf. As of now,I will make a small script to work with Kubuntu, but we need the Fn keys to be working for many people who don't want to be running scripts all the time for such a simple task.

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