When using the MacBook Pro in Closed Clamshell mode (especially with the older Thunderbolt Display), the brightness controls on either the keyboard or System Preferences stop working. Some of the solutions from other users are:

  • Unplug the Thunderbolt cable and plug it back in
  • Installing a third-party app like “Brightness Slider”

I figured there must be a way to do this from the terminal and a quick search returned a beautiful little CLI tool called “brightness”:

brew install brightness

And now I’m able to change the brightness with something like:

brightness 0.6