EC2 instance stops immediatly after start

It sounds like there may be an issue with your bash script or how it's being executed at startup that's causing your EC2 instance to stop prematurely. Here are a few things to check and try:

1. Review your bash script: Make sure the script isn't exiting or calling a shutdown command immediately. Check for any errors or unexpected behavior at the beginning of the script.

2. Check system logs: After attempting to start the instance, check the system logs for any error messages or indications of why the instance is stopping. You can access these logs through the EC2 console or by attaching the root volume to another instance.

3. Test the script manually: Try running the script manually when logged into the instance to see if it executes correctly and doesn't cause an immediate shutdown.

4. Use EC2 User Data: Instead of using crontab, consider using EC2 User Data to run your script at instance launch. This might provide more visibility into any issues.

5. Add logging to your script: Implement logging in your script to track its execution and identify where it might be failing or causing the instance to stop.

6. Check instance status: In the EC2 console, look at the "State transition reason" for more information about why the instance stopped.

7. Verify IAM permissions: Ensure that the IAM role associated with your EC2 instance has the necessary permissions to perform all actions in your script.

8. Consider using nohup: If your script is designed to run in the background, use nohup to prevent it from being terminated when the session ends.

If these steps don't resolve the issue, you may need to create a new instance from your AMI without the problematic crontab entry, then carefully re-implement and test your startup script.

Remember, it's crucial to thoroughly test any startup scripts or automated processes in a non-production environment before implementing them on critical instances.

Sources
Why does my EC2 stop 10 minutes after being automatically started via Lambda? | AWS re:Post
Troubleshoot Linux instance that automatically shuts down | AWS re:Post