Question

A DevOps team deploys a fleet of EC2 instances using a CloudFormation template. They want the instances to install packages, write configuration files, and start services automatically at launch, with the ability to update this configuration by simply updating the CloudFormation stack. They also want a clean signal to CloudFormation indicating whether the bootstrap configuration succeeded, so a failed configuration causes the stack update to roll back. Which approach best meets these requirements using native CloudFormation capabilities?

Accepted Answer

Define the configuration in the AWS::CloudFormation::Init metadata on the instance resource, run cfn-init in the UserData to apply it, and use cfn-signal with a CreationPolicy/UpdatePolicy so CloudFormation waits for and evaluates the success signal.

Answer

Embed all package installs and file writes as a bash script in the UserData block, and rely on the instance reaching the 'running' state as the success indicator for CloudFormation.

Answer

Store the configuration commands in an SSM Parameter Store hierarchy and use a Lambda-backed custom resource to SSH into each instance and apply the changes during stack updates.

Answer

Bake all configuration into a golden AMI and reference the AMI ID in the template, updating the AMI ID parameter whenever configuration changes are required.