title: Running Docker pull command in Dockerfile
body: <p>I am new to Docker and trying some things. Now I want to create a Dockerfile, which build automatically the Oracle DB image. </p>
  
  <pre><code>############################################################
  # Dockerfile to build MongoDB container images
  # Based on Ubuntu
  ############################################################
  
  # Set the base image to Ubuntu
  FROM ubuntu
  
  # File Author / Maintainer
  MAINTAINER Example McAuthor
  
  # Update the repository sources list
  RUN apt-get update
  
  ################## BEGIN INSTALLATION #####################
  CMD docker pull alexeiled/docker-oracle-xe-11g
  </code></pre>
  
  <p>My problem is the <code>docker pull</code> command.<br>
  When I try to use the <code>RUN</code> command, the docker daemon say, that he can't find '<code>docker</code>'. Then I use the <code>CMD</code> command, and it works, but is that correct? Maybe you can show me alternative ways. </p>