Xrandr

Xrandr allows you to manipulate query and manipulate display settings.

Position/Resolution

xrandr --output VGA-1 --mode 1920x1080   # set resolution
xrandr                                   # query outputs/modes
xrandr --listmonitors                    # list outputs

xrandr --output VGA1 --off \
       --output HDMI1 --off \
       --output LVDS1 --left-of HDMI1 --auto

Brightness

xrandr --output LVDS1 --brightness 0.7