Fixing screen brightness on Thinkpad X201 and Ubuntu 10.10

I just tried installing Ubuntu 10.10 on my Thinkpad X201. For the most part, everything worked right away and on an SSD drive, it felt blazingly fast.

However, the screen brightness controls did not work. Some online research suggested adding acpi_osi=Linux to the kernel boot parameters and I also found a tip in the thinkpad-acpi driver documentation for how to force-enable it (over the native Linux ACPI driver).

First, edit your /etc/default/grub file to add acpi_osi=Linux and acpi_backlight=vendor arguments to GRUB_CMDLINE_LINUX_DEFAULT. It should look something like this:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi=Linux acpi_backlight=vendor"

Then run sudo update-grub to enable the new arguments. After a reboot, my brightness controls were working.

The other thing I noted was a strange error on boot: “failed to get i915 symbols”. I found a solution for that, too:

sudo -s
echo "i915" >> /etc/initramfs-tools/modules
update-initramfs -k all -u
reboot

For more general information about Linux on the Thinkpad X201, see ThinkWiki.