Make a new EC2 instance on Elastic Beanstalk

Hi !

With eb ssh, you can specify the instance ID with the -i option:
https://docs.aws.amazon.com/elasticbeanstalk/latest/dg/eb3-ssh.html

If you want to always run extra scripts on your starting instances, I recommend you one of those four options:

1. Use Docker
   https://docs.aws.amazon.com/elasticbeanstalk/latest/dg/create_deploy_docker.html
   https://docker.io
   https://docker-curriculum.com

2. Create your AMI
   https://docs.aws.amazon.com/elasticbeanstalk/latest/dg/using-features.customenv.html

3. Use a custom platform
   https://docs.aws.amazon.com/elasticbeanstalk/latest/dg/custom-platforms.html

4. Use .ebextensions config files.
   It can give you advanced features: for example, if there are some scripts that you want to run only on one instance, you can use the leader_only command in a .ebextensions file.
   https://docs.aws.amazon.com/elasticbeanstalk/latest/dg/ebextensions.html

Finally, for how the auto-scaling works, there are different strategies possible you can choose from, you can see how Auto-Scaling Groups do it here:
https://docs.aws.amazon.com/elasticbeanstalk/latest/dg/using-features.managing.as.html

I hope this will help you in your journey with Elastic Beanstalk.

Have a good day,

Haks

Thanks for the help. For SSH, I discovered that if you have more than one EC running, eb ssh actually asks you which one you want to connect to.

I am confused by the rest of your answer. I had already stated that I have extra scripts running -- I didn't mention that they were provided by ebextensions.

As for the "how to see if my script works", all I did was go to the EC2 console and forcefully terminate the two running instances. This forced Amazon to make new ones -- from there, I could see that everything did work, and my custom scripts actually ran.