title: In elastic beanstalk, how do I run a command before the container is launched?
body: <p>I'm using the a single container docker version of Elastic Beanstalk to deploy a ruby on rails application (my docker is pre-built).
  The docker image specifies a CMD of "rails server".</p>
  
  <p>I would like to issue "rake db:migrate" just before the "rails server" is run. Is there a way to do it using elastic beanstalk configuration or otherwise?</p>