anchor.diff:  * `APP-NAME`: The name of the app being pushed
   * `REPO`: The name of the repository where the image is stored
   * `IMAGE`: The name of an image from Docker Hub
  -* `TAG`: (Optional) The tag or version for the image
  +* `TAG`: (Optional, recommended) The tag or version for the image
   
   For example, the following command pushes the `my-image` image from Docker Hub to a Cloud Foundry app:
   
  
positive.code: * A registry that supports the [Docker Registry HTTP API V2](https://docs.docker.com/registry/spec/api/) and presents a valid certificate for HTTPS traffic.
  
  <p class="note"><strong>Note</strong>: If you want to log in to your app container using the <code>cf ssh</code> command, a shell such as <code>sh</code> or <code>bash</code> must be available in the container. The SSH server in the container looks for the following executables in absolute locations or the <code>PATH</code> environment variable: <code>/bin/bash</code>, <code>/usr/local/bin/bash</code>, <code>/bin/sh</code>, <code>bash</code>, and <code>sh</code>.</p>
  
  ## <a id='port_config'></a>Port Configuration
  
  
negative.code: <p class="note"><b>Note</b>: For information about specifying <code>MY-REGISTRY-URL</code>, see <a href="https://cloud.google.com/container-registry/docs/pushing-and-pulling">Pushing and Pulling Images</a> on the Google Cloud documentation.</p>
  
  ##<a id='volume'></a> Docker Volume Support
  You can use volume services with Docker apps. For more information about enabling volume support, see the [Using an External File System (Volume Services)](../services/using-vol-services.html) topic.
  