How do I turn off the notification light on front of phone

Use the following command:

echo 1 > /sys/class/leds/green/brightness

It switches green led on. Change 'green' to 'red' or 'blue' to switch other color leds on. And change '1' to '0' if wanna switch it off. Root is not needed, permissions do alow any user play with leds including the flashlight and keys backlight ones.