How to change the Monitor brightness on Linux?

The ddcutil application can change an external monitor's actual backlight brightness via the VESA DDC/MCCS standard (xrandr can only move the X11 output within a monitor's currently set limits, it can't change the actual backlight brightness). This should work for any monitors that support that capability via Display Data Channel (DDC has been around for some time, it is be widely supported, but for external monitors only). I use ddcutil to automatically adjust my monitor based on the ambient light level sampled from a webcam. Ddcutil uses the i2c-dev kernel module (modprobe i2c-dev or set it to load at boot).

ddcutil detect                    # Get list of DDC displays
ddcutil --display 2 capabilities  # List VCP feature key numbers
ddcutil --display 2 getvcp 10     # Get brightness by key number
ddcutil --display 2 setvcp 10 50  # Set brightness to 50                                                                            

Here is the simple step to control brightness in Linux based system

First, you have to know the monitoring screen connected you.

To know this run this command

xrandr -q

It will give useful information about the screen

( Here my screen connected to eDP, It might be different for your system )

After knowing that run the below command

xrandr --output eDP --brightness [0-10]

Replace eDP by your connected screen from the above output.

you can choose normal brightness values from 0.1 to 1.0

command for this:

xgamma -gamma 0.7