How to edit the GRUB file

The backlight of my Acer Aspire 5336 screen turns off when Ubuntu 12.04 is installed. I found that it could be corrected by editing the GRUB fileScreen turns black after booting, backlight only works in recovery mode on an Acer Aspire 5736z

But since I cannot do so via Ubuntu (as the backlight is turned off) how can I edit the GRUB file?

Thank you

2 Answers

Why don't you try to edit the file using a external monitor?

Because if you can't edit the file and update Grub with the actual installation, you have to bind the installed OS using a LiveCD or LiveUSB () and then edit the /etc/default/grub and update Grub.

You could boot to a live CD and edit GRUB that way, or you can do it whilst in GRUB itself, much faster:

• Highlight "Ubuntu" in the GRUB menu, but rather than hitting Return to boot Ubuntu, hit the letter e. This will take you to an editor.

If you never see a list of operating systems to boot, holding Shift as the computer loads will display it.

• Add acpi_osi=Linux acpi_backlight=vendor at the end of the second-to-last line, as shown in the picture:

• Hit F10, which will boot Ubuntu, backlight and all.

• You can then make the change permanent by following the instructions in the answer you referred to.