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Remediation

Follow these steps to migrate an Auto Scaling Group from a legacy Launch Configuration to a Launch Template.

From Command Line​

Export the Existing Launch Configuration​

aws autoscaling describe-launch-configurations \
    --launch-configuration-names {{launch-configuration-name}} \
    --query 'LaunchConfigurations[0]' \
    --output json > {{lc-export.json}}

Note: Modify the JSON schema to match the Launch TempTemplate since the configuration object includes extra fields that EC2’s create-launch-template will reject, and some keys need renaming.

Create the Launch Template​

aws ec2 create-launch-template \
    --launch-template-name {{launch-template-name}} \
    --version-description {{version-description}}  \
    --launch-template-data file://{{lc-export.json}}

Update the Auto Scaling Group to Use the Launch Template​

aws autoscaling update-auto-scaling-group \
    --auto-scaling-group-name {{asg-name}} \
    --launch-template LaunchTemplateId={{launch-template-id}},Version='$Latest'

After this update, any new instances will be provisioned using the new Launch Template.

Replace Existing Instances (Optional)​

To roll out the new template across all running instances, initiate an Instance Refresh:

  1. Create a JSON file ({{config.json}}) with your preferences.

    Example of config.json:

    "AutoScalingGroupName": "asg-name",
    "Preferences": {
      "InstanceWarmup": 60,
      "MinHealthyPercentage": 50,
      "AutoRollback": true,
      "ScaleInProtectedInstances": Ignore,
      "StandbyInstances": Terminate
    }
}
  1. Start the instance refresh:
aws autoscaling start-instance-refresh \
    --cli-input-json file://{{config.json}}