title: pg_dump server and pg_dump version mismatch in docker
body: <p>When I run the command <code>psql --version</code> within the <code>railsApp</code> container, I get <code>9.4.12</code> and when I run the same within the <code>postgres</code> container, I get <code>9.6.2</code>. How can I get the versions to match?</p>
  
  <p>I am getting the following error when I try to do a migration on Rails App which does a <code>pg_dump</code> sql import.</p>
  
  <pre><code>pg_dump: server version: 9.6.2; pg_dump version: 9.4.12
  pg_dump: aborting because of server version mismatch
  rails aborted!
  </code></pre>
  
  <p>Here's my Docker-compose.yml file:</p>
  
  <pre><code>version: "2.1"
  services:
    railsApp:
      build:
        context: ./
      ports:
        - "3000:3000"
      links:
        - postgres
      volumes:
        - .:/app
    postgres:
      image: postgres:9.6
      ports:
        - "5432:5432"
      volumes:
        - ./.postgres:/var/lib/postgresql
  </code></pre>
  
  <p>The Dockerfile:</p>
  
  <pre><code>FROM ruby:2.3.3
  
  # setup /app as our working directory
  RUN mkdir /app
  WORKDIR /app
  
  # Replace shell with bash so we can source files
  RUN rm /bin/sh &amp;&amp; ln -s /bin/bash /bin/sh
  
  # Set debconf to run non-interactively
  RUN echo 'debconf debconf/frontend select Noninteractive' | debconf-set-selections
  
  # Install base dependencies
  
  FROM ruby:2.3.3
  
  # setup /app as our working directory
  RUN mkdir /app
  WORKDIR /app
  
  # Replace shell with bash so we can source files
  RUN rm /bin/sh &amp;&amp; ln -s /bin/bash /bin/sh
  
  # Set debconf to run non-interactively
  RUN echo 'debconf debconf/frontend select Noninteractive' | debconf-set-selections
  
  # Install base dependencies
  RUN apt-get update &amp;&amp; apt-get install -y -q --no-install-recommends \
          apt-transport-https \
          build-essential \
          ca-certificates \
          curl \
          git \
          libssl-dev \
          python \
          rsync \
          software-properties-common \
          wget \
          postgresql-client \
          graphicsmagick \
      &amp;&amp; rm -rf /var/lib/apt/lists/*
  
  # Install node and npm with nvm
  RUN curl https://raw.githubusercontent.com/creationix/nvm/v0.33.0/install.sh | bash
  
  ENV NVM_DIR=/root/.nvm
  ENV NODE_VERSION v7.2.1
  
  ENV NODE_PATH $NVM_DIR/versions/node/$NODE_VERSION
  ENV PATH      $NODE_PATH/bin:./node_modules/.bin:$PATH
  
  
  RUN source $NVM_DIR/nvm.sh \
      &amp;&amp; nvm install $NODE_VERSION \
      &amp;&amp; nvm alias default $NODE_VERSION \
      &amp;&amp; nvm use default
  
  # Install our ruby dependencies
  ADD Gemfile Gemfile.lock /app/
  RUN bundle install
  
  # copy the rest of our code over
  ADD . /app
  
  ENV RAILS_ENV development
  ENV SECRET_KEY_BASE a6bdc5f788624f00b68ff82456d94bf81bb50c2e114b2be19af2e6a9b76f9307b11d05af4093395b0471c4141b3cd638356f888e90080f8ae60710f992beba8f
  
  # Expose port 3000 to the Docker host, so we can access it from the outside.
  EXPOSE 3000
  
  # Set the default command to run our server on port 3000
  CMD ["rails", "server", "-p", "3000", "-b", "0.0.0.0"]
  </code></pre>