Prevent ubuntu from starting a DNS server on port 53

Works on ubuntu 18.04 LTS.

Edit: /etc/systemd/resolved.conf to change the DNS and DNSStubListener settings.

DNS=8.8.8.8
DNSStubListener=no

sudo ln -sf /run/systemd/resolve/resolv.conf /etc/resolv.conf

sudo systemctl restart systemd-resolved