DDNS Updater

A lightweight dynamic DNS updater for Cloudflare written in Go. Automatically detects your public IP changes and updates specified DNS A records.

Features

• Automatic public IP detection with fallback services
• Multiple subdomain support
• Cloudflare API v4 integration
• Configurable check intervals
• Retry logic with exponential backoff
• Structured JSON logging
• Graceful shutdown handling
• Cross-platform (Linux, macOS)

Quick Start

1. Generate configuration template

make init-config

This creates config.yaml with default settings.

2. Get Cloudflare credentials

Generate API Token

1. Log in to Cloudflare Dashboard
2. Go to Profile → API Tokens
3. Click Create Token
4. Use the Edit zone DNS template or create a custom token with:
   • Permissions: Zone → DNS → Edit, Zone → Zone → Read
   • Zone Resources: Include → Specific zone → (select your domain)
5. Copy the token (you'll only see it once)

Find Zone ID

1. In Cloudflare Dashboard, select your domain
2. Scroll down on the Overview page
3. Find Zone ID in the right sidebar under API section
4. Copy the Zone ID

3. Configure

Edit config.yaml:

cloudflare:
  api_token: "your-token-here"          # From step 2
  zone_id: "your-zone-id-here"          # From step 2
  zone_name: "example.com"              # Your domain
  subdomains:
    - name: "home"                      # Updates home.example.com
      proxied: false
    - name: "vpn"
      proxied: true                     # Route through Cloudflare proxy

4. Run locally (test)

make run

Logs will show IP detection and DNS updates in real-time.

Production Deployment

Linux (systemd)

Install and set up service

# Build and install binary
make install-linux

# Edit config with your credentials
sudo nano /etc/ddns-updater/config.yaml

# Create systemd service
make service-linux

# Enable and start
sudo systemctl daemon-reload
sudo systemctl enable ddns-updater
sudo systemctl start ddns-updater

# Check status
sudo systemctl status ddns-updater

# View logs
sudo journalctl -u ddns-updater -f

Service management

sudo systemctl stop ddns-updater      # Stop service
sudo systemctl restart ddns-updater   # Restart service
sudo systemctl disable ddns-updater   # Disable auto-start

macOS (launchd)

Install and set up service

# Build and install binary
make install-macos

# Edit config with your credentials
sudo nano /usr/local/etc/ddns-updater.yaml

# Create launchd service
make service-macos

# Load and start
launchctl load ~/Library/LaunchAgents/com.ddns-updater.plist
launchctl start com.ddns-updater

# View logs
tail -f /usr/local/var/log/ddns-updater.log

Service management

launchctl stop com.ddns-updater       # Stop service
launchctl unload ~/Library/LaunchAgents/com.ddns-updater.plist  # Unload service

Configuration Reference

# Check interval in minutes (how often to check for IP changes)
check_interval: 5

cloudflare:
  api_token: "your-api-token"
  zone_id: "your-zone-id"
  zone_name: "example.com"
  subdomains:
    - name: "subdomain"
      proxied: false  # true = route through Cloudflare proxy (orange cloud)

logging:
  file: "ddns-updater.log"
  level: "info"  # debug, info, warn, error

retry:
  max_attempts: 3
  delay_seconds: 5

webhook:
  enabled: false
  url: ""  # Optional webhook for notifications

Building from Source

# Build for current platform
make build

# Build for all platforms
make build-all

# Clean build artifacts
make clean

Built binaries will be in ./bin/

Troubleshooting

Authentication errors

• Verify API token has correct permissions (Zone → DNS → Edit, Zone → Zone → Read)
• Confirm token is scoped to the correct zone
• Check token hasn't expired

DNS record not found

• Ensure zone_name matches your Cloudflare domain exactly
• Verify subdomain exists in Cloudflare DNS settings
• Check subdomain name doesn't include the domain (use home, not home.example.com)

Service won't start

Linux:

sudo journalctl -u ddns-updater -n 50

macOS:

cat /usr/local/var/log/ddns-updater.err

Docker deployment

Build the image:

docker build -t yourname/ddns-updater:latest .

Run with a local config file:

cp config.yaml.example config.yaml   # or make init-config
# edit config.yaml with your Cloudflare settings

docker run -d \
  --name ddns-updater \
  --restart unless-stopped \
  -v $(pwd)/config.yaml:/config/config.yaml:ro \
  yourname/ddns-updater:latest

Or with Docker Compose:

docker compose up -d

The container runs in the foreground inside Docker; restarts are handled by Docker’s restart policy.