先来看看3个文件：
/sys/class/backlight/acpi_video0/actual_brightness
/sys/class/backlight/acpi_video0/brightness
/sys/class/backlight/acpi_video0/max_brightness
大家尽管望文生义：
actual_brightness 当前亮度值，其值和brightness一样
brightness 亮度值，改变它的值即可改变显示器背光亮度
max_brightness 亮度的取值范围的最大值
装了Linux，如果按Fn组合键不能修改屏幕亮度，试试这样:
echo N > /sys/class/backlight/acpi_video0/brightness
(N为数字，取值范围为 0<=N<=max_brightness)
举例：
su - root
cd /sys/class/backlight/acpi_video0
echo 7 > brightness
cat max_brightness > brightness
