https://www.duckdns.org/

https://www.duckdns.org/about.jsp
https://www.duckdns.org/spec.jsp
https://www.duckdns.org/why.jsp

https://www.duckdns.org/install.jsp
https://gist.github.com/taichikuji/6f4183c0af1f4a29e345b60910666468

https://www.duckdns.org/faqs.jsp