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I have a Debian Linux desktop. I want to change the screen's brightness without pressing the brightness button of my monitor. How can I do this? is this possible in command line or is there an application to be installed?

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unix.stackexchange.com might be better than Super User, but there is not migration link pointing that way. – dmckee Mar 11 '11 at 3:39
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So you have a desktop with an external monitor and you want to control the backlight, right? It is connected by VGA cable? I don't think there is a way to do that. Most LCD backlight controls are for laptops and handhelds that have direct access (I/O) to the backlight controller. I don't think there is a control path via the VGA interface for that. – Keith Mar 11 '11 at 7:31
ADditional info: I'm using CRT monitor. – Neilvert Noval Mar 11 '11 at 17:06
@NeilvertNoval Instead of commenting with add. info, add the info to the original question. The fact that it is a CRT monitor should be declared in the question title itself. – hesse Jan 12 at 13:09
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3 Answers

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You could give this solution a try:

echo -n 100 > /proc/acpi/video/VGA/LCD/brightness

Also, in the comments, there are some hints what to do alternatively if it doesn't work (f.e. using GLX0 instead of VGA.

EDIT: As this doesn't seem to help, another user in the comments suggests to install xbacklight and calling xbacklight -set 100.

EDIT2: And another one says if you don't have a video folder, try sudo modprobe video.

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I checked on this before posting, but I have no video folder on that path. – Neilvert Noval Mar 9 '11 at 14:47
modprobe video -> command not found – Neilvert Noval Mar 10 '11 at 16:01
I already installed xbacklight, but when I do xbacklight -set 100. it says No outputs have backlight property – Neilvert Noval Mar 10 '11 at 16:02
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up vote 0 down vote

Look under /sys/class/backlight for the appropriate files to frob.

echo -n 6 > /sys/class/backlight/acpi_video0/brightness
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my /sys/class/backlight is an empty directory. – Neilvert Noval Mar 11 '11 at 17:05
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up vote 0 down vote

If you don't have hardware support for changing the brightness of your monitor you could use the command xrandr together with its option flags --output and --brightness, as can be seen in my answer to a similar question on askubuntu.com

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