I have an AMI that I use for my rails web servers. This AMI using an EBS Snapshot to launch with the basics all ready for production. 

I now need to update some configuration settings on web servers (nginx.conf). I can easily ssh into a box and update the settings but then future launched instances don't have the settings as they use an older snapshot.

How do I go about making it so that new ec2 instances launch with the new settings. I'm guessing I need to update the snapshot? How do I go about updating the snapshot which all the web server ec2 instances use?

Thanks