DNS Updater

A small CLI that updates existing A records on supported DNS providers to match the current IP of your machine (either its public “WAN” IP or the IP of a local network interface).

Runs once and exits — ideal to schedule with cron or a systemd timer.

Features

• Update existing A records on multiple providers in one run
• Providers: DigitalOcean, Vultr
• Public IP lookup via pluggable services (ipecho, jsonip, etc.)
• Resolve IP from a local interface (e.g., eth0)
• Skips updates when the record is already up-to-date
• Structured, human-readable logging

How It Works

• Loads the YAML config and registers DNS providers.
• Selects the configured public IP lookup service.
• Iterates updates and, for each record:
  • Resolves the target IP from wan (public IP) or a local interface name.
  • Looks up the existing record by name on the provider.
  • Updates the record only if the IP changed.

Only A records are listed/updated; records must already exist.

Install

• Requirements: Go 1.23+ (module toolchain sets go1.24.1).

Build with Makefile:

make build

Or directly with Go:

go build -v -o build/dnsupdater cmd/dnsupdater/main.go

Configuration

See config.example.yml for a full example. Create your own config.yml alongside the binary (or pass -config):

services:
  IPLookup: ipecho   # one of: ipecho, jsonip, ifconfig.me, ip.me, icanhazip

providers:
  digitalocean:
    token: <YOUR_DO_TOKEN>
  vultr:
    token: <YOUR_VULTR_TOKEN>

updates:
  digitalocean:
    domain1.com:
      www: wan        # use public IP
      app: eth0       # use IP from local interface
    domain2.com:
      www: wan
  vultr:
    example.com:
      www: wan

• services.IPLookup: public IP lookup backend. Supported values: ipecho, jsonip, ifconfig.me, ip.me, icanhazip.
• providers: map of provider name to credentials. Current providers: digitalocean, vultr.
• updates: which domains/records to update per provider.
  • Value must be either wan (public IP) or a local interface name (e.g., eth0).

Known limitation: literal IPv4 strings in updates (e.g., 84.24.254.21) are not interpreted as IPs and will fail; use wan or an interface name instead.

Usage

./build/dnsupdater -config ./config.yml     # run once
./build/dnsupdater -v                       # print version

Logs are written to stderr in a readable format.

Scheduling

• Cron: */5 * * * * /path/to/dnsupdater -config /path/to/config.yml >/dev/null 2>&1
• systemd (example): create a service and timer that invoke the binary every few minutes.

Testing

make test

Provider Notes

• DigitalOcean: updates existing A records via the Domains API.
• Vultr: updates existing A records via the DNS API.
• Records must already exist; creation is not implemented.

Troubleshooting

• “Invalid DNS service”: the name under updates: doesn’t match a configured provider.
• “Failed to fetch ip”: wan lookup failed or the local interface name is wrong.
• No change: when the on-file IP matches the resolved IP, the tool logs success without making an API call.

License

AGPL-3.0-only. See LICENSE.