I recently upgraded my laptop to a brand new Lenovo Y410P and promptly replaced Windows 8 with a Linux install. Unfortunately I immediately ran into a very strange driver(?) issue where, on boot, the computer would default to the absolute lowest screen brightness level. This meant that I would need to manually adjust the screen brightness up just to see the login screen. Thankfully after some help from the excellent people over on the Ubuntu Forums I managed to find a very easy work around.
1) As root open up /etc/default/grub
I did this by simply issuing the following command:
sudo nano /etc/default/grub
2) Find the line that says GRUB_CMDLINE_LINUX= and add “acpi_backlight=vendor” to the list of options.
3) From a terminal run this command to update GRUB
That’s pretty much it. My computer now boots with the correct screen brightness as one would expect.