Which solution will meet these requirements with the MOST operational efficiency?
In the CloudFormation template, create an AWS::SSM::Document resource that joins the EC2 instance to the AWS Managed Microsoft AD domain by using the parameters for the existing directory. Update the launch template to include the SSMAssociation property to use the new SSM document. Attach the AmazonSSMManagedInstanceCore and AmazonSSMDirectoryServiceAccess AWS managed policies to the IAM role that the EC2 instances use.
In the CloudFormation template, update the launch template to include specific tags that propagate on launch. Create an AWS::SSM::Association resource to associate the AWS-JoinDirectoryServiceDomain Automation runbook with the EC2 instances that have the specified tags. Define the required parameters to join the AWS Managed Microsoft AD directory. Attach the AmazonSSMManagedInstanceCore and AmazonSSMDirectoryServiceAccess AWS managed policies to the IAM role that the EC2 instances use.
Store the existing AWS Managed Microsoft AD domain connection details in AWS Secrets Manager. In the CloudFormation template, create an AWS::SSM::Association resource to associate the AWS-CreateManagedWindowsInstanceWithApproval Automation runbook with the EC2 Auto Scaling group. Pass the ARNs for the parameters from Secrets Manager to join the domain. Attach the AmazonSSMDirectoryServiceAccess and SecretsManagerReadWrite AWS managed policies to the IAM role that the EC2 instances use.
Store the existing AWS Managed Microsoft AD domain administrator credentials in AWS Secrets Manager. In the CloudFormation template, update the EC2 launch template to include user data. Configure the user data to pull the administrator credentials from Secrets Manager and to join the AWS Managed Microsoft AD domain. Attach the AmazonSSMManagedInstanceCore and SecretsManagerReadWrite AWS managed policies to the IAM role that the EC2 instances use.
Explanations:
While this option creates an SSM document to join the EC2 instances to the AWS Managed Microsoft AD, it relies on the SSMAssociation property in the launch template. This can add complexity and does not align as well with the use of tagging and automatic associations for operational efficiency.
This option effectively uses tags to identify EC2 instances and associates them with the AWS-JoinDirectoryServiceDomain Automation runbook. This method is efficient as it utilizes existing SSM capabilities without requiring user data or complex configurations, making it more manageable and scalable in operations.
This approach introduces unnecessary complexity by requiring the creation of an SSM Association with the AWS-CreateManagedWindowsInstanceWithApproval runbook. It also involves passing ARNs from Secrets Manager, which is not the most straightforward method for joining the domain. Additionally, the need for approval in the runbook can create operational overhead.
While this option retrieves credentials from Secrets Manager in user data, it requires manual scripting and adds complexity to the EC2 launch process. This method is less efficient than using SSM runbooks or associations, as it relies on user data execution, which can lead to inconsistencies and is less scalable in dynamic environments.
I reckon the answer is:
In the CloudFormation template, update the launch template to include specific tags that propagate on launch. Create an AWS::SSM::Association resource to associate the AWS-JoinDirectoryServiceDomain Automation runbook with the EC2 instances that have the specified tags. Define the required parameters to join the AWS Managed Microsoft AD directory. Attach the AmazonSSMManagedInstanceCore and AmazonSSMDirectoryServiceAccess AWS managed policies to the IAM role that the EC2 instances use.