## `docker-compose.yml`

```yml
services:
  ddns:
    environment:
      - API_TOKEN=
      - ZONE_ID=
      - RECORD_ID=
      - DOMAIN_NAME=
    image: python:slim
    restart: unless-stopped
    stop_grace_period: 0s
    container_name: ddns
    entrypoint: python -c
    command:
      - |
        import os; os.system('pip install -q requests 2>/dev/null')
        import json, time, requests

        def get_current_ip():
            return requests.get('https://api64.ipify.org').text

        def update_dns(ip):
            zone_id = os.environ['ZONE_ID']
            record_id = os.environ['RECORD_ID']
            api_token = os.environ['API_TOKEN']
            domain_name = os.environ['DOMAIN_NAME']

            url = f"https://api.cloudflare.com/client/v4/zones/{zone_id}/dns_records/{record_id}"
            headers = { 
                'Authorization': f'Bearer {api_token}'
            }

            data = {
                'type': 'A',
                'name': domain_name,
                'content': ip,
                'ttl': 1,
                'proxied': False
            }

            response = requests.put(url, headers=headers, json=data)

            if response.status_code == 200:
                print(f"DNS 레코드가 성공적으로 업데이트되었습니다. 새 IP: {ip}", flush=True)
            else:
                print("DNS 레코드 업데이트에 실패했습니다.", flush=True)
                print(response.text, flush=True)

        last_ip = None
        check_interval = 6 * 3600  # 6시간

        while True:
            current_ip = get_current_ip()
            if current_ip != last_ip:
                print(f"IP 변경 감지: {last_ip} -> {current_ip}", flush=True)
                update_dns(current_ip)
                last_ip = current_ip
            else:
                print(f"IP 변경 없음: {current_ip}", flush=True)

            time.sleep(check_interval)
```