How to prevent screen from going black (back light is shut down) at startup (laptop) Ubuntu 12.04?

Question

So,in may laptop with Ubuntu 12.04, the startup is like this:

1) I see the Ubuntu logo with the 5 dots on a purple background for a few seconds.

2) The screen goes completely black (no back light), but it's not shut down, i can still see shadows.

3) The system is fully loaded (i can log-in), but the screen is still shadowy (no back light).

4) I have to wait about 1 minute (logged or not) for the back light to turn on.

How do I prevent the system from shutting the back light at startup ?

Answer 1

Open a Terminal window (Ctrl+Alt+T) and run this command to open GRUB's main configuration file in nano (a non-graphical text editor):

sudo nano /etc/default/grub

In the text editor, find this line:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

Add acpi_backlight=vendor to the end, so it looks like this:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"

Save the file and quit the text editor, by pressing Ctrl+o followed by Ctrl+x. Then run:

sudo update-grub

Done. Backlight will be at full strength by default.