title: How do I update new instances started by AWS auto scaling?
body: <p>We use AWS cloudformation service to initialize our stack, and set up the auto scaling service to bring up new app servers when load is rising. </p>
  
  <p>My understanding is that Auto Scaling can only start predefined AMI as new instances. These instances could be different from other running instances, because we may have updated packages/source code deployed on those instances.</p>
  
  <p>How can I bring the new instances up-to-date?
  Should I update the AMIs everytime I deploy something new to the running instances? Or is there anyway to trigger auto-deployment on new instances (Opsworks) when auto scaling?</p>
  
  <p>I am new to AWS, so pardon me if my question is rudimentary.</p>