How to Disable second screen in Ubuntu

On update, ubuntu shows 2 screen as default.

Here is fix

xrandr | grep connected

sudo nano /etc/lightdm/monitor1-off.sh

#!/bin/bash  
 xrandr --output HDMI1 --off #change HDMI1 with your device id ( you can check by executing command 'xrandr'

sudo chmod +x /etc/lightdm/monitor1-off.sh

Edit /etc/lightdm/lightdm.conf and add the following line to the file

greeter-setup-script=/etc/lightdm/monitor1-off.sh

It will remove 2nd screen on OS starting.