udm-ddns-reconnect

A tiny Dockerized Node.js service that:

• checks your external IP every 5 minutes (configurable)
• updates your ddnss.de record only when the IP changes
• triggers a nightly UniFi Dream Machine Pro reconnect via SSH (cron-based)

Features

• ✅ No DDNS spam: updates only on IP change (state persisted to /data/state.json)
• ✅ Nightly reconnect via SSH command (default: killall -HUP pppd)
• ✅ Runs well on Raspberry Pi 5 (arm64) and x86_64 (multi-arch images via GitHub Actions)
• ✅ Timezone-aware cron (default: Europe/Berlin)

---

Configuration

All configuration is done via environment variables.

Required (DDNS)

Variable	Description
DDNS_USER	ddnss.de username
DDNS_PASSWORD	ddnss.de password
DDNS_HOST	hostname to update (e.g. myhost.ddnss.de)

Optional (DDNS)

Variable	Default	Description
DDNS_UPDATE_URL	https://www.ddnss.de/upd.php	Update endpoint (for IPv4/IPv6 prefer https://ip4.ddnss.de/upd.php / https://ip6.ddnss.de/upd.php)
CHECK_INTERVAL_MINUTES	5	IP check interval
IP_SERVICE_URL	https://api.ipify.org	External IP service URL
DATA_DIR	/data	Persistent data directory

Optional (Nightly reconnect)

Variable	Default	Description
RECONNECT_ENABLED	true	Enable/disable reconnect
RECONNECT_CRON	0 5 * * *	Cron schedule (minute hour day month weekday)
TZ	Europe/Berlin	Timezone for cron scheduling
SSH_HOST		UDM host/IP
SSH_PORT	22	SSH port
SSH_USER		SSH username (often root)
SSH_PASSWORD		SSH password
SSH_COMMAND	/usr/bin/killall -HUP pppd	Command executed on the UDM

Important: If your passwords contain special characters (e.g. #, !, :), quote them in YAML or use a .env file.

---

Run with Docker Compose

Create a docker-compose.yml:

services:
  udm-ddns-reconnect:
    image: ghcr.io/huftierchen/udm-ddns-reconnect:latest
    container_name: udm-ddns-reconnect
    restart: unless-stopped
    environment:
      TZ: "Europe/Berlin"

      # DDNS
      DDNS_USER: "YOUR_DDNS_USER"
      DDNS_PASSWORD: "YOUR_DDNS_PASSWORD"
      DDNS_HOST: "yourhost.ddnss.de"
      DDNS_UPDATE_URL: "https://ip4.ddnss.de/upd.php"
      CHECK_INTERVAL_MINUTES: "5"
      IP_SERVICE_URL: "https://api.ipify.org"

      # Reconnect
      RECONNECT_ENABLED: "true"
      RECONNECT_CRON: "31 4 * * *"   # daily 04:31
      SSH_HOST: "192.168.1.1"
      SSH_PORT: "22"
      SSH_USER: "root"
      SSH_PASSWORD: "YOUR_SSH_PASSWORD"
      SSH_COMMAND: "/usr/bin/killall -HUP pppd"
    volumes:
      - udm_ddns_state:/data

volumes:
  udm_ddns_state:

Start:

docker compose up -d
docker logs -f udm-ddns-reconnect

---

Build locally (optional)

docker build -t udm-ddns-reconnect:local .
docker run --rm -it \
  -e DDNS_USER=... -e DDNS_PASSWORD=... -e DDNS_HOST=... \
  -e SSH_HOST=... -e SSH_USER=... -e SSH_PASSWORD=... \
  -v udm_ddns_state:/data \
  udm-ddns-reconnect:local

GitHub Actions (multi-arch image to GHCR)

This repo is build and published as a multi-arch image (linux/arm64, linux/amd64) to GitHub Container Registry using GitHub Actions.

Notes / Troubleshooting

ddnss says “parameters missing”

Usually means one of DDNS_USER, DDNS_PASSWORD, DDNS_HOST is empty or got cut off by YAML parsing. Use quotes, or .env.

SSH: “All configured authentication methods failed”

• verify username/password are correct
• ensure password is not being truncated by YAML (# needs quotes!)
• UDM may use keyboard-interactive auth; the app supports this already.