title: postgresql docker replications
body: <p>I'm relatively new to dockers, but I'm kind of wondering whether is it possible for me to create two master-slave postgres containers. I can do it on virtual machines, but I'm a bit confused on the one in docker. </p>
  
  <p>If it's possible can someone please point me to right directions? 
  I have tried to docker exec -it, but all the files are all missing and I cannot edit the files inside. </p>