I have a slightly old Gateway NV series laptop, and just installed Ubuntu 14.04 LTS because Windows was getting slow. Once it installed though, I found that the screen backlight does not come on after it reaches the boot screen. It works during the BIOS page, but goes off after. The screen itself works, because I can see the images if I put a bright flashlight up to it. Right now and during the install, I have been using an HDMI connection to my TV, which works perfectly, but just can't get the back light to function on the laptop. Using the backlight settings or hotkeys does nothing, and it shows no available drivers I can download. What can I do to fix this? My laptop is using a Mobile Intel® GM45 Express Chipset for graphics and a Intel® Core™2 Duo CPU T6600 @ 2.20GHz × 2 processor. Thank you for any help.
This has to do with the ACPI backlight driver for your specific video card in your laptop. Google Search "Forcing backlight on linux"
The Ubuntu wiki has a section dedicated to forcing the back light on. https://wiki.ubuntu.com/Kernel/Debugging/Backlight