Fix the backlight on laptops using Intel video chipsets

There are issues with some Intel video cards xserver-xorg-video-intel and KMS and the default 2.6.32 kernel in Debian squeeze.

On my Intel-equipped Asus netbook booting from GRUB or starting an X session can result in a black screen and completely unresponsive system. A temporary fix is to edit the booting GRUB entry and add acpi=off to the kernel line.

A more permanent fix is to configure the backlight by editing GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub:

GRUB_CMDLINE_LINUX_DEFAULT="quiet acpi_osi=Linux acpi_backlight=vendor"

Update the grub configuration by running sudo update-grub2 and reboot.

Increase the brightness setting to maximum visibility. For example ... on my netbook I run:

$ sudo echo 15 > /sys/class/backlight/eeepc/brightness

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