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To work around bug #1005495 (changing LCD brightness via hotkeys impossible), I'd like to have one command line query for increasing and one for reducing the brightness of my LCD. I could then map a hotkey to each one of this queries.

The problem is: I don't know how to increase and reduce the LCD brightness on the command line. Do you?

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possible duplicate of Unable to change brightness in a Lenovo laptop –  Lekensteyn Jun 10 '12 at 17:30
Thanks, Lekensteyn, but it's not a duplicate since lsmod | grep ^i915 gives me no output (see accepted solution). Still looking for a solution. –  user69748 Dec 14 '12 at 11:56

8 Answers 8

one more way we have to do this is with another new program named as xbacklight , open your terminal and type this

sudo apt-get install xbacklight

then type this xbacklight -set 50

there 50 stands for brightness range we can get it upto 100 from 0 .

you can also increase and decrease the brightness from present value to specified level.as you mentioned if you want to increase to 10% from current value of brightness then you can give this

xbacklight -inc 10

and to decrease 10% you can give this

xbacklight -dec 10 
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+1 for simplicity. –  zpletan Jun 11 '12 at 5:31
Looks like a really simple command but what I'd need is something like xbacklight -increase 10 to increase the brightness by 10 percent. Is that possible, too? –  user69748 Aug 24 '12 at 9:31
Yes you can. I've already mention that . so you can get that by xbacklight -inc 10 –  Raja Aug 24 '12 at 16:53
Ok, now it's in your answer. Thanks a lot, I'll try that out. –  user69748 Aug 27 '12 at 7:28
That really looks simple, but unfortunatelly it doesn't work for me. Brightness simply doesn't change, not with -dec and not with -set. I guess I'll have to hope the bug gets fixed any time soon. Thanks nevertheless. –  user69748 Sep 4 '12 at 14:38

Open your terminal and type this

xrandr -q | grep " connected"

it will gives you the output as LVDS1 connected 1680x1050+0+0 (normal left inverted right x axis y axis) 331mm x 207mm

There LVDS1 Stands for your display .

so now you have to do as

xrandr --output LVDS1 --brightness 0.5

there 0.5 stands for brightness and it ranges from 0.0 to 1.0 . 0.0 -> Full black .so you have to choose the required value of brightness .

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Thanks for you answer but what I'd need is something like xrandr --increase 10 to increase the brightness by 10 percent. Is that possible, too? –  user69748 Dec 14 '12 at 11:50
@user69748 well, you could use my first answer for that purpose . –  Raja Dec 14 '12 at 17:21
thanks but that doesn't work for me as written there. –  user69748 Jan 17 '13 at 16:01
this doesn't seem to change the brightness at a hardware level –  user84207 Oct 18 '13 at 6:29
Elaborate the issue please –  Raja Oct 18 '13 at 6:36

The following works for me:

echo 400 > /sys/class/backlight/intel_backlight/brightness

I guess the maximum possible value is in the /sys/class/backlight/intel_backlight/max_brightness file.

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for Laptops
sudo setpci -s 00:02.0 F4.B=80
change 80 by [0-FF] to get lowest-highest brightness The value specified is in hex, so 80 will give you a 50% brightness

for Desktop [not tested by ME]
xgamma -gamma .75

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Thanks for you answer but what I'd need is something like setpci --increase 10 to increase the brightness by 10 percent. Is that possible, too? –  user69748 Dec 14 '12 at 11:50
thank you for this answer, it's good to know how things are done at the lower levels –  user84207 Oct 18 '13 at 6:30
This was the only answer that worked for me on a Samsung NB30 Plus. –  OSE Oct 21 '13 at 18:33
I can't seem to get this to work.. Should I change some parameters, perhaps, and if so, how do I find the appropriate values? –  Rasmus Oct 2 '14 at 8:27

Try this in terminal:

xrandr --output LVDS1 --brightness 0.9

You can change the last value as you like, eg. 0.2

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1) Output is not always LVDS1, but user can find out with xrandr --verbose 2) Doesn't change backlight intensity –  user84207 Oct 18 '13 at 6:31

Here's a short line that can help you relax your eyes. Just create a crontaab with the line or make a script

xrandr --output VGA1 --brightness 0.5; sleep 20; xrandr --output VGA1 --brightness 1
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KDE 4.12:

qdbus org.kde.Solid.PowerManagement /org/kde/Solid/PowerManagement/Actions/BrightnessControl setBrightness 55
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can you explain what It will do ? –  Raja Apr 8 '14 at 18:27

As @palacsint said, echo 244 > /sys/class/backlight/intel_backlight/brightness path works for me.

But max and min values are resent in /sys/class/backlight/intel_backlight/max_brightness and /sys/class/backlight/intel_backlight/bl_power files respectively.

Also, the actual brightness that your computer is running now is present in /sys/class/backlight/intel_backlight/actual_brightness

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protected by Raja Apr 23 '14 at 13:28

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