This project was written specifically to run on the Raspberry Pi Zero W and update records with the local IP addresses assigned to the Pi. It likely works on any platform supported by Go, however.

ddns is a small Go library for dynamically updating DNS records.

Currently the only DNS provider included is Cloudflare, but the ddns.Provider interface is a single method if you would like to wrap your own provider's API.

package main

import (
	"context"
	"log"
	"os"

	"github.com/Travis-Britz/ddns"
)

func main() {
	c, err := ddns.New(
		"dynamic-local-ip.example.com",
		ddns.NewCloudflare(os.Getenv("CLOUDFLARE_ZONE_TOKEN")),
		ddns.UsingResolver(ddns.InterfaceResolver("eth0")),
	)
	if err != nil {
		log.Fatalf("error creating ddns client: %s", err)
	}
	ctx := context.Background()
	err = c.RunDDNS(ctx)
	if err != nil {
		log.Fatalf("dns update failed: %s", err)
	}
}

More examples: https://pkg.go.dev/github.com/Travis-Britz/ddns#pkg-examples

ddnscf is a small command line tool for dynamically updating Cloudflare DNS records.

Using go install:

go install github.com/Travis-Britz/ddns/cmd/ddnscf@latest

Other:

build ddns/cmd/ddnscf and then move the build binary to your preferred location (with execute permissions).

Once the program is in place, run it. It will prompt for a Cloudflare API token and then store it to a file. The token must have Zone.DNS:Edit permissions.

To skip the prompt you may create the key file in advance with the proper file permissions:

echo "MyVerySecretDNSToken" > ~/.cloudflare && chmod 600 ~/.cloudflare

ddnscf -h:

Usage of ddnscf:
-d string
        The domain name to update
-k string
        Path to cloudflare API credentials file (default "~/.cloudflare")
-ip string
        Set a specific IP address
-url string
        Use a public IP lookup URL
-if string
        Use a specific network interface
-i string
        Interval duration between runs (default 5m0s)
-once
        Run once and exit
-v
        Enable verbose logging

Update a domain with all of the local IPs assigned to the Pi:

ddnscf -v -d pi1.example.com

Update a domain with the IPs for a specific network interface:

ddnscf -v -d pi1.example.com -if wlan0

Update a domain with our public IP (using a lookup service):

ddnscf -v -d pi1.example.com -url https://ipv4.icanhazip.com

url must speak HTTP and respond "200 OK" with an IP address as the first line of the response body.

Update a domain once with a specific IP:

ddnscf -v -d pi1.example.com -ip 192.168.0.2 -once

Update a domain every minute:

ddnscf -v -d pi1.example.com -i 1m

Create the service file:

cd /lib/systemd/system
sudo touch ddnscf.service

Add the contents:

[Unit]
Description=Keep DNS records updated
After=network-online.target
Wants=network-online.target

[Service]
ExecStart=/usr/bin/ddnscf -d pi1.example.com -k /home/pi/.cloudflare
User=pi

[Install]
WantedBy=multi-user.target

sudo systemctl daemon-reload
sudo systemctl enable ddnscf.service

Configuring devices or the router on the network where this ddns client resides to use Cloudflare's 1.1.1.1 DNS resolver service will further reduce DNS propagation time in the event of IP changes.