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I am unable to change the brightness of my desktop screen using this path. System settings{top right corner of the screen)>Under Personal Brightness & lock.No option to change brightness is available here.In Ubuntu 11.04 Shift key + +/- key was used to change brightness,the same doesn't work in 12.04.

Also under System settings{top right corner of the screen)>Under Hardware Displays,my monitor is recognized as a Laptop despite me using a desktop!

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2 Answers 2

in acer aspire 5741 I add edit in GRUB_CMDLINE_LINUX to :

GRUB_CMDLINE_LINUX="quiet splash pcie_aspm=force i915.i915_enable_rc6=1 acpi_osi=Linux acpi_backlight=vendor"

and it is work well

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Only the acpi_backlight=vendor part is important. The rest allies only to your system, which the OP may not have. –  hexafraction Oct 8 '12 at 17:05
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Give this a try

sudo gedit /etc/default/grub

Find the line line

GRUB_CMDLINE_LINUX=""

and change it to

GRUB_CMDLINE_LINUX="acpi_osi=Linux"

Update your GRUB

sudo update-grub

Restart your system . Hope this works with you

I used to have the same problem and trying this half solved the problem , the directions work opposite but the brightness works...kind of workaround

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