recently I'm trying Ubuntu OS which has been installed on my USB stick.
And I found that my screen brightness is too high.
In order to resolve this issue,
apt-get install xbacklight
after that, I can use my laptop's hot key to adjust the brightness of screen.
This makes me feel good,
but, while I found the touchpad isn't work well on 3, 4 finger gesture,
I was upset, again :(