title: Why containers being removed after build?
body: <p>I build my project with following <code>Dockerfile</code>:</p>
  
  <pre><code>FROM ubuntu:14.04
  
  #"updating package repos.."
  RUN apt-get update
  
  #"installing required packages.."
  RUN apt-get -y install python2.7-dev build-essential python-pip
  run apt-get -y install libjpeg-dev libpng3 libpng12-dev
  run apt-get -y install nodejs npm nodejs-legacy
  run npm install -g peer
  run apt-get -y install supervisor
  
  #"creating sites folder under /opt"
  run mkdir /opt/sites
  
  #"copying project into /opt/sites"
  add project-latest /opt/sites/project-latest
  
  #"copying supervisor conf into /etc/supervisor/conf.d"
  add etc/project.conf /etc/supervisor/conf.d/
  
  #"installing virtualenv"
  run pip install virtualenv
  
  #"change working dir to /opt/sites/project-latest"
  workdir /opt/sites/project-latest
  
  #"create vritualenv folder named 'env' "
  run virtualenv env
  
  #"activating environment"
  run . env/bin/activate
  
  #"installing packages into env from requirements.txt"
  run pip install -r requirements.txt
  
  #"syncing DB"
  run python manage.py syncdb
  
  #"migrating DB"
  run python manage.py migrate
  
  #"update and restart supervisorctl"
  run service supervisor start
  cmd supervisorctl reread
  cmd supervisorctl update
  cmd supervisorctl restart all
  
  #"expose 8000 and 9000 ports"
  expose 8000
  expose 9000
  </code></pre>
  
  <p>And this is the final output of build process:</p>
  
  <pre><code>Successfully built 29dbd8e8bb0a
  Removing intermediate container 8a20545921e0
  Removing intermediate container 0da63841f6ad
  Removing intermediate container fab164fe93c2
  Removing intermediate container 77b61eceef36
  Removing intermediate container 87a24b079f47
  Removing intermediate container cb2520749e30
  Removing intermediate container 9e9c54376433
  Removing intermediate container 130f6eaeed6a
  Removing intermediate container 56f9d93a1e75
  Removing intermediate container 599b10008caa
  Removing intermediate container eab7598a5e95
  Removing intermediate container c31b58fcc405
  Removing intermediate container 8b4a55fbb345
  Removing intermediate container 13b35d86044e
  Removing intermediate container 0ab10eef8f5e
  Removing intermediate container ebf42d9493f1
  Removing intermediate container 70c772c4aa73
  Removing intermediate container fe5039bfbe15
  Removing intermediate container 8f9a93cd5438
  Removing intermediate container 2d673cf029f8
  Removing intermediate container ab8485d09ee7
  Removing intermediate container 0fdfa200ac27
  Removing intermediate container d2d02358e25d
  </code></pre>
  
  <p>If I create a container to run <code>bash</code> inside my built image, I see some of the build steps are forgotten. i.e, there is no virtual environment with my <code>requirements.txt</code> file.</p>
  
  <p>And I have no idea how to open my running <code>Django</code> application from my host machine. There are no any ports or IP info either. </p>