title: AWS EC2 instances with auto scaling staying in sync
body: <p>I have a Node.js web application currently running on a single EC2 instance on AWS. I am thinking of using auto scaling with 2 or more EC2 instances since the load on the application is increasing. </p>
  
  <p>I have been trying to understand something with AWS Auto Scaling for a couple hours now but I cant seem to find an answer anywhere. </p>
  
  <p>Currently, at many instances I SSH into my Ubuntu EC2 instance to modify some things or to run a deploy command (which grabs latest code from github). How does this work when you have, let's say 4 instances running under the auto scaling? </p>
  
  <p>So if I SSH into a server and change the server.js file, what happens to the other 3 instances?</p>
  
  <p>If that is not possible what are my choices? I have seen many people seeing that using S3 is the way to keep things in Sync but I don't fully get that. So I have to keep all my source code in S3 and do my edits from there?</p>