title: Docker: MeteorJS gets installed twice with some warnings
body: <p>I am using a <code>ubuntu:latest</code> image to create a meteorJS docker image.
  The problem is, that meteor is downloaded twice and I do get some warnings for package.json.</p>
  
  <p><em>Dockerfile</em></p>
  
  <pre><code>FROM ubuntu:latest
  
  # build arguments
  ARG APP_PACKAGES
  ARG APP_LOCALE=en_US
  ARG APP_CHARSET=UTF-8
  ARG APP_USER=app
  ARG APP_USER_DIR=/home/${APP_USER}
  
  # set the locale (required by Meteor)
  RUN locale-gen ${APP_LOCALE}
  RUN localedef ${APP_LOCALE}.${APP_CHARSET} -i ${APP_LOCALE} -f ${APP_CHARSET}
  
  # create a non-root user that can write to /usr/local (required by Meteor)
  RUN useradd -mUd ${APP_USER_DIR} ${APP_USER}
  RUN chown -Rh ${APP_USER} /usr/local
  USER ${APP_USER}
  
  # MeteorJS
  RUN curl https://install.meteor.com/ | sh
  
  # NPM packages
  WORKDIR '/builds/project/data'
  RUN meteor npm install gridfs-stream gm fluent-ffmpeg
  </code></pre>
  
  <p>And the last part (<code>RUN meteor ...</code>) gives me this:</p>
  
  <pre><code>This is your first time using Meteor!
  Installing a Meteor distribution in your home directory.
  Downloading Meteor distribution
  </code></pre>
  
  <p>So meteor is downloaded twice:</p>
  
  <ol>
  <li>curl ...</li>
  <li>meteor npm install ...</li>
  </ol>
  
  <p>Also I do get this warning:</p>
  
  <pre><code>npm WARN enoent ENOENT: no such file or directory, open '/builds/project/data/package.json'
  npm WARN media No description
  npm WARN media No repository field.
  npm WARN media No README data
  npm WARN media No license field.
  </code></pre>
  
  <p>Why should there be a package.json, although I do not use <code>--save</code>?</p>