zigbee2mqtt dynamic configuration.yaml with env variable substitution (e.g. for dynamic configuration via balena.io cloud)

configuration.yaml.env

# Environment variables are escaped by the envsubst entrypoint

homeassistant: false
permit_join: $ZIGBEE2MQTT_PERMIT_JOIN
mqtt:
  base_topic: zigbee2mqtt
  server: 'mqtt://mqtt'
serial:
  port: $ZIGBEE2MQTT_SERIAL_PORT

# Write auto-generated data to other files
devices: devices.yaml
groups: groups.yaml

docker-compose.yml

version: '2'
services:  
  mqtt:
    image: eclipse-mosquitto
    volumes:
      - mosquitto_data:/mosquitto/data
      - mosquitto_log:/mosquitto/log

  zigbee2mqtt:
    image: koenkk/zigbee2mqtt
    volumes:
      # Overwrite configuration.yaml with env-var-substituted version of configuration.yaml.env on every startup
      - ./:/custom
      - zigbee2mqtt_data:/app/data
    entrypoint: /custom/envsubst.sh
    depends_on:
      - mqtt
    privileged: true
    environment:
      TZ: Europe/Berlin
      # Uncomment for local development.
      # Comment when deploying to balena.io - it does not support env var substitution in compose file
      # ZIGBEE2MQTT_PERMIT_JOIN: "${ZIGBEE2MQTT_PERMIT_JOIN}"
      # ZIGBEE2MQTT_SERIAL_PORT: "${ZIGBEE2MQTT_SERIAL_PORT}"

volumes:
  db:
  zigbee2mqtt_data:
  mosquitto_data:
  mosquitto_log:

envsubst.sh

#!/bin/sh
# Interpolate (substitute) environment variables in configuration.yaml.env.
# Write the result to /app/data/configuration.yaml

INPUT=/custom/configuration.yaml.env
OUTPUT=/app/data/configuration.yaml

( echo "cat <<EOF" ; cat "$INPUT" ; echo EOF ) | sh > "$OUTPUT"

./run.sh