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I had Ubuntu 12.10 on my PC, and I did the upgrade to Ubuntu 13.10. But now I have a problem with brightness control, it is always on maximum level and I can't set it neither with fn nor with brightness control in the system settings nor with xbacklight or other method.

I had tried changing GRUB_CMDLINE_LINUX_DEFAULT value, but nothing happens.

How can I fix this problem?

I have ubuntu 13.10 64bit, kernel 3.11.0-13, on a Toshiba Portege R930, Processor: Intel® Core™ i7-3520M CPU @ 2.90GHz × 4; Graphic: Intel® Ivybridge Mobile

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you may try this command: sudo su -c "echo 110 >/sys/class/backlight/intel_backlight/brightness", of course you may change 110 to any arbitrary value – microarm15 Nov 6 '13 at 13:30

I added GRUB_CMDLINE_LINUX="acpi_backlight=vendor" into /etc/defaults/grub, updated grub and restarted PC.

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This also fixes the brightness bug that is present in 12.04 with other hardware, this repaired the brightness issue on my Precise machine. – Thomas Ward Nov 6 '13 at 13:55

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