EC2 Auto-Scaling Instances Retaining Old Data After Termination

Potential Causes: Reusing EBS Volumes:

If your auto-scaling group is configured to attach existing EBS volumes to new instances, the new instances could retain data from the terminated instances.

AMI Configuration:

If your Auto Scaling group uses a custom Amazon Machine Image (AMI) that includes pre-existing data or configurations, new instances will launch with this data.

User Data Scripts:

If you have user data scripts configured for your instances, they might be downloading or copying data from a central repository upon launch.

CloudFormation Templates:

If you're using CloudFormation, check the templates to ensure they are not configured to attach existing resources (like EBS volumes).

Instance Termination Protection:

Ensure that termination protection is not enabled, which can prevent instances from being terminated correctly.

**Troubleshooting Steps:

Check EBS Volume Attachments:**

Verify if your auto-scaling group configuration includes settings that attach existing EBS volumes to new instances. Adjust the settings to ensure new instances use fresh volumes.

Review AMI:

Inspect the AMI used by your auto-scaling group. Ensure it is a clean image without the unwanted backups and changes.

Inspect User Data Scripts:

Check your user data scripts to see if they are pulling in the old data or performing operations that result in data persistence. Auto Scaling Group Configuration:

Review the auto-scaling group’s launch configuration or launch template. Ensure it’s configured to use a fresh AMI and that no old volumes are being reused. CloudFormation Stack:

If applicable, review your CloudFormation stack to ensure it’s not set to reuse existing resources unintentionally.

Activity Logs:

Investigate the auto-scaling activity logs in detail. The absence of instance launch logs could indicate an issue with the auto-scaling policies or the health checks.

Detailed Steps:

Check EBS Volume Attachments:

Open the EC2 console.

Navigate to “Auto Scaling Groups.”

Select the group experiencing issues.

Check the launch configuration or launch template for any settings that specify existing EBS volume attachments.

Review AMI:

Open the EC2 console.

Navigate to “AMIs” under the “Images” section.

Identify the AMI used by the auto-scaling group and ensure it’s a clean image.

Inspect User Data Scripts:

Open the EC2 console.

Navigate to “Auto Scaling Groups.”

Select the group and review the launch configuration or launch template.

Check the user data script for any commands that might be pulling in old data.

Review Auto Scaling Group Configuration:

Open the EC2 console.

Navigate to “Auto Scaling Groups.”

Select the group and review all configurations, particularly the launch configuration or launch template.

Investigate CloudFormation Stack:

Open the CloudFormation console.

Identify the stack related to the auto-scaling group.

Review the stack template for any settings that might cause the reuse of existing resources.

Review Auto Scaling Activity Logs:

Open the EC2 console.

Navigate to “Auto Scaling Groups.”

Select the group and view the activity history to understand the termination and launch events.