How to setup Let's Encrypt for Nginx on Ubuntu 16.04 (including IPv6, HTTP/2 and A+ SLL rating)

There are two main modes to run the Let's Encrypt client (called Certbot):

  • Standalone: replaces the webserver to respond to ACME challenges
  • Webroot: needs your webserver to serve challenges from a known folder.

Webroot is better because it doesn't need to replace Nginx (to bind to port 80).

In the following, we're setting up HTML is served from /var/www/mydomain, and challenges are served from /var/www/letsencrypt.