Reduce Brightness from command line on KaliLinux:

Go to the console and download the following package:

  • cd /root/Desktop
  • wget http://ftp.de.debian.org/debian/pool/main/x/xcalib/xcalib_0.8.dfsg1-2_amd64.deb
  • sudo dpkg -i xcalib_0.8.dfsg1-2_amd64.deb

Then enter the following command:

  • xcalib -co 40 -a

To reset

  • xcalib -c

Done.