Google Cloud Dynamic DNS Client

Syncs the current IP address to Google Cloud DNS records. Can discover your public IP based on (1) a 3rd party web service, (2) directly from the local network interface, or (3) the network router using UPnP.

Works only for IPv4 addresses.

This project is distributed as a Docker image. (Or if you're familiar with Golang, you may build it from source yourself.)

Using

Run this application's container using the command sync and restart policy always. That will sync the IP address automatically whenever it changes.

At minimum, configure the environment variables DNS_NAMES, GOOGLE_PROJECT and GOOGLE_APPLICATION_CREDENTIALS. If you change the MODE from its default, you'll also need to set the container's network mode to host.

For a list of other commands, run the help command.

Example Docker Compose configuration

version: '2.4'
services:
  dyndns:
    image: luontola/gcp-dynamic-dns:1.5
    command: sync
    network_mode: host
    environment:
      DNS_NAMES: example.com. www.example.com.
      GOOGLE_PROJECT: example-123456
      GOOGLE_APPLICATION_CREDENTIALS: /gcp-keys.json
    volumes:
      - /path/to/gcp-dns-admin-keys.json:/gcp-keys.json:ro
    restart: always

Environment variables

MODE (optional)

The method for determining your public IP address. Possible values:

• service (default) - Asks a 3rd party web service for your external IP address.
• interface - Asks your operating system for the IP address assigned to a network interface.
• upnp - Asks your network router for its external IP address using Universal Plug and Play.
  • Not every router has UPnP enabled and a firewall may block it as well, so to debug issues, first check if upnpc -s reports the ExternalIPAddress.

Default: service

SERVICE_URLS (optional, MODE=service)

Web addresses of services which report your public IP address. Multiple services may be separated by space, in which case they will be used in a round-robin fashion. The continuous check interval is 5 minutes, so use more than once service to call each individual service less often.

Default: https://ipv4.icanhazip.com/ https://checkip.amazonaws.com/ https://ifconfig.me/ip https://ipinfo.io/ip

INTERFACE_NAME (optional, MODE=interface)

Name of the network interface whose IP to use. If not defined, the program will detect the primary network interface automatically.

Example: eth0

DNS_NAMES

List of domain names to update. Separate the domain names with one space. Each name must end with a period. The DNS records must already exist on Cloud DNS and they must be type A records.

Example: example.com. subdomain.example.com. example.org.

GOOGLE_PROJECT

The name of your Google Cloud project. The above mentioned DNS names must be hosted under this project's Cloud DNS.

Example: your-project-123456

GOOGLE_APPLICATION_CREDENTIALS

Path to service account credentials with permissions to update your Cloud DNS records.

Example: /path/to/dns-updater-gcp-keys.json

In the GCP console, under IAM & admin > Service accounts, create a service account for the application. Name it dns-updater, grant it the DNS > DNS Administrator role, create a key for it in JSON format and save it as dns-updater-gcp-keys.json.

Developing

Run tests and build the project

docker-compose build --force-rm

Run the application

docker-compose run --rm app help

The application container doesn't have sh or other fancy stuff, so to inspect its contents use the docker export command:

docker export <container> | tar tv