title: Create multiple users inside of docker image when container starts
body: <p>Let me see if I can explain myself better than the tile.</p>
  <p>I am creating an image that will have an smtp GW and a imap/pop3d service to allow users to send/receive emails. What I want to do is have my container read a file (usernames i will generate passwords 'randomly' when creating the user) when it starts and create the user accounts for those users.</p>
  <p>I will export something like</p>
  <p>/data/conf</p>
  <p>and there will be a file with a list of users. Now I want to read that file at start and create each user there.</p>
  <p>Is this even possible? Are there easier ways to accomplish this? Any help will be appreciated.</p>