title: Docker error cannot delete docker container, conflict: unable to remove repository reference
body: <p>I want to remove the container at Docker, but an error occurs when you want to delete</p>
  
  <p>My next step before removing the container, see the list of existing container</p>
  
  <pre><code>sts@Yudi:~/docker$ sudo docker ps -as
  
  CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS                    PORTS               NAMES                  SIZE
  78479ffeba5c        ubuntu              "/bin/bash"         42 hours ago        Exited (0) 42 hours ago                       sharp_wescoff          81 B (virtual 187.7 MB)
  0bd2b54678c7        training/webapp     "python app.py"     5 days ago          Exited (0) 5 days ago                         backstabbing_ritchie   0 B (virtual 323.7 MB)
  0adbc74a3803        training/webapp     "python app.py"     5 days ago          Exited (143) 5 days ago                       drunk_feynman          0 B (virtual 323.7 MB)
  </code></pre>
  
  <p>one I want to delete the list, namely <strong>"training / webapp"</strong>
  but an error that occurred</p>
  
  <pre><code>sts@Yudi:~/docker$ sudo docker rmi training/webapp
  Error response from daemon: conflict: unable to remove repository reference "training/webapp" (must force) - container 0bd2b54678c7 is using its referenced image 54bb4e8718e8
  Error: failed to remove images: [training/webapp]
  </code></pre>
  
  <p>Whether the container is running in the images?</p>
  
  <p>Please help</p>