title: Docker Compose file is invalid, additional properties not allowed
body: <p>This is my sample docker-compose.yml file.</p>
  
  <pre><code>version: '2'
  config-server:
    image: ccc/config-server
    restart: always
  registration-server:
    image: ccc/registration-server
    restart: always
    ports:
      - 1111:1111
  </code></pre>
  
  <p>When I use <code>docker-compose up -d</code> I get an error: </p>
  
  <pre><code>"ERROR: The Compose file './docker-compose.yml' is invalid because:
  Additional properties are not allowed ('registration-server', 'config-server' were unexpected)
  
  You might be seeing this error because you're using the wrong Compose file version. Either specify a version of "2" (or "2.0") and place your service definitions under the `services` key, or omit the `version` key and place your service definitions at the root of the file to use version 1.
  For more on the Compose file format versions, see https://docs.docker.com/compose/compose-file/
  </code></pre>