Abbreviated version of setting up x11vnc on Ubuntu 16.04 based systems:
sudo x11vnc -storepasswd /etc/x11vnc/passwd
sudo vi /lib/systemd/system/x11vnc.service
[Unit]
Description=Start x11vnc at startup.
After=multi-user.target
[Service]
Type=simple
ExecStart=/usr/bin/x11vnc -xkb -auth /var/run/lightdm/root/:0 -noxrecord -noxfixes