Windows Services Stopping After Reboot or Scaling Down on EC2 Instance

This issue with Windows services stopping after rebooting or scaling down an EC2 instance could be caused by several factors. Here are some potential reasons and troubleshooting steps you can take:

1. System resources: When scaling down, the instance may not have enough resources to start all services. Check if the scaled-down instance has sufficient CPU, memory, and disk space to run all 12 services.

2. Service dependencies: Ensure that all required dependencies for your services are starting correctly. Some services may fail to start if their dependencies are not available.

3. Windows updates: Recent Windows updates might have affected service configurations. Check the Windows Update history and see if any recent updates coincide with the start of this issue.

4. Application or driver conflicts: New application installations or driver updates could interfere with service startups. Review recent changes to the instance.

5. Corrupted service configurations: The service configurations might have become corrupted. Try reconfiguring the services that are failing to start.

6. EC2Config service: Ensure that the EC2Config service is up-to-date and functioning correctly. This service manages various tasks during instance startup and can affect other services.

7. Instance metadata service: Verify that the instance can reach the EC2 metadata service. Issues with metadata retrieval can cause problems with instance startup and service initialization.

8. Auto Scaling group settings: Review your Auto Scaling group configurations to ensure they're not interfering with service startups during scale-down events.

To troubleshoot:

1. Check Windows Event Viewer for any error messages related to the services that are stopping.
2. Use PowerShell or the command prompt to retrieve recent system events that might provide clues about the shutdowns or reboots.
3. Review the service logs for the affected services to identify any specific errors preventing them from starting.
4. Test launching a new instance with the same configuration to see if the issue persists, which could help isolate whether it's an instance-specific problem or a broader configuration issue.

If the problem continues after these steps, you may need to engage AWS support for further assistance, especially if you suspect it's related to the EC2 infrastructure or Auto Scaling functionality.
Sources
Why did my EC2 Windows instance shut down or reboot | AWS re:Post
Troubleshoot EC2 Windows instance status check failures | AWS re:Post
Troubleshoot Amazon EC2 Windows instance start issues - Amazon Elastic Compute Cloud
Troubleshoot unhealthy instances in Amazon EC2 Auto Scaling - Amazon EC2 Auto Scaling