title: Duplicate images with same id in Docker
body: <p>When I download the image with docker-compose file, the images are duplicated. 
  Here is my docker-compose.yml</p>
  
  <pre>
  version: "3"
  services:
  
     ubuntu:
        build: ./linux
        container_name: ubuntu
        stdin_open: true
        tty: true
  </pre>
  
  <p>My Dockerfile in linux folder</p>
  
  <pre>
  FROM ubuntu
  </pre>
  
  <p>The output of the command "$docker images":</p>
  
  <pre><code>REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
  ubuntu              latest              ccc7a11d65b1        9 days ago          120 MB
  ubuntu_ubuntu       latest              ccc7a11d65b1        9 days ago          120 MB
  
  </code></pre>
  
  <p>Why this duplicity?</p>