1. Remove the default Vino server:
$ sudo apt-get -y remove vino
  1. Install x11vnc:
$ sudo apt-get -y install x11vnc
  1. Create the directory for the password file:
$ sudo mkdir /etc/x11vnc
  1. Create the encrypted password file:
$ sudo x11vnc --storepasswd /etc/x11vnc/vncpwd

You will be asked to enter and verify the password. Then press Y to save the password file.

  1. Create the systemd service file for the x11vnc service:
$ sudo nano /lib/systemd/system/x11vnc.service

Copy/Paste this code into the empty file:

[Unit]
Description=Start x11vnc at startup.
After=multi-user.target

[Service]
Type=simple
ExecStart=/usr/bin/x11vnc -auth guess -forever -noxdamage -repeat -rfbauth /etc/x11vnc/vncpwd -rfbport 5900 -shared

[Install]
WantedBy=multi-user.target

6: Reload the services:

$ sudo systemctl daemon-reload
  1. Enable the x11vnc service at boot time:
$ sudo systemctl enable x11vnc.service
  1. Start the service:

Either reboot or

$ sudo systemctl start x11vnc.service

Reference