Comment 24 for bug 280518

The contents of each of those files is "7". (If it makes any difference,
I had the laptop plugged in to AC power which makes the brightness go up
as high as it can during POST).

The command that started with "echo 2" did nothing because I prefixed it
with "sudo" and it still wouldn't let me edit it. I edited it with Kate
and nothing changed, not sure if I have to log out after I change that
file or not.

Steve Langasek wrote:
> Jeremy,
>
> Please check the contents of the following files:
>
> $ cat /sys/devices/virtual/backlight/acpi_video0/brightness
> $ cat /sys/devices/virtual/backlight/acpi_video0/max_brightness
> $ cat /sys/devices/virtual/backlight/acpi_video0/actual_brightness
>
> and as root, try to change the value of the 'brightness' file:
>
> # echo 2 > /sys/devices/virtual/backlight/acpi_video0/brightness
>
> Does this change the brightness of your display?
>