If the laptop's default brightness adjustment keys are not working, then add a boot time linux kernel parameter and try again. But here we'll focus on the command line tools.
There's many GUI tool like XFCE Power Manager, to adjust the brightness. Each method usability is depending on the hardware platform you're using like a laptop or desktop. Here we'll discus about few different method to control brightness the same. Using Xrandr command to adjust Linux screen brightness
