There are many dynamic DNS (DDNS) providers, but I could not find one that supports updating records using nsupdate. This guide will show how to set up a DDNS service on your own server as well as how to integrate it with macOS to automatically push updates whenever the machine IP changes.

First, install Knot DNS on the server. Once installed, you’ll need to generate a TSIG key that will be used for authenticating updates to the DDNS server. To do so, run keymgr -t tsig.example.com. This will print a configuration that looks like the following:

The next step is to add it to knot.conf, which will most likely be in /etc/knot/knot.conf. Add the key configuration, followed by an accompanying ACL rule and the zone information:

Ensure the server is listening on all interfaces to be able to access it externally:

To integrate with macOS’s built-in DDNS client, you’ll need to add one more record. To do so, run:

knotc zone-begin example.com
knotc zone-set example.com _dns-update._udp 600 SRV 0 0 53 example.com.
knotc zone-commit example.com

Lastly, to enable DDNS on macOS, open Sharing in System Settings, and click Edit in the hostname section at the end. Enable Use dynamic global hostname, and fill the details as follows: