Native parameter support for Amazon Machine Image IDs

When you create a String parameter, you can specify the data type as aws:ec2:image to ensure that the parameter value you enter is a valid Amazon Machine Image (AMI) ID format.

Support for AMI ID formats lets you avoid updating all your scripts and templates with a new ID each time the AMI that you want to use in your processes changes. You can create a parameter with the data type aws:ec2:image, and for its value, enter the ID of an AMI. This is the AMI from which you currently want new instances to be created. You then reference this parameter in your templates, commands, and scripts.

For example, you can specify the parameter that contains your preferred AMI ID when you run the Amazon Elastic Compute Cloud (Amazon EC2) run-instances command.

Note

The user who runs this command must have AWS Identity and Access Management (IAM) permissions that include the ssm:GetParameters API action in order for the parameter value to be validated. Otherwise, the parameter creation process fails.

aws ec2 run-instances \
    --image-id resolve:ssm:/golden-ami \
    --count 1 \
    --instance-type t2.micro \
    --key-name my-key-pair \
    --security-groups my-security-group

You can also choose your preferred AMI when you create an instance using the Amazon EC2 console. For more information, see Using a Systems Manager parameter to find an AMI in the Amazon EC2 User Guide for Windows Instances.

When it's time to use a different AMI in your instance creation workflow, you need only update the parameter with the new AMI value, and Parameter Store again validates that you have entered an ID in the proper format.

Grant permissions to create a parameter of aws:ec2:image data type

Using AWS Identity and Access Management (IAM) policies, you can provide or restrict user access to Parameter Store API actions and content.

The following example policy grants users permission to call the PutParameter API operation for aws:ec2:image. This means that the user can add a parameter of data type aws:ec2:image to the system.

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "VisualEditor0",
            "Effect": "Allow",
            "Action": "ssm:PutParameter",
            "Resource": "*"
        },
        {
            "Sid": "VisualEditor1",
            "Effect": "Allow",
            "Action": "ec2:DescribeImages",
            "Resource": "*"
        }
    ]
}

How AMI format validation works

When you specify aws:ec2:image as the data type for a parameter, Systems Manager does not create the parameter immediately. It instead performs an asynchronous validation operation to ensure that the parameter value meets the formatting requirements for an AMI ID, and that the specified AMI is available in your AWS account.

It is important to note that a parameter version number may be generated before the validation operation is complete. That is, a parameter version number being generated alone isn't an indication that the operation has completed successfully.

To monitor whether your parameters are created successfully, we recommend using Amazon EventBridge to send you notifications about your create and update parameter operations. These notifications report whether a parameter operation was successful or not. If an operation fails, the notification includes an error message that indicates the reason for the failure.

{
    "version": "0",
    "id": "eed4a719-0fa4-6a49-80d8-8ac65EXAMPLE",
    "detail-type": "Parameter Store Change",
    "source": "aws.ssm",
    "account": "111122223333",
    "time": "2020-05-26T22:04:42Z",
    "region": "us-east-2",
    "resources": [
        "arn:aws:ssm:us-east-2:111122223333:parameter/golden-ami"
    ],
    "detail": {
        "exception": "Unable to Describe Resource",
        "dataType": "aws:ec2:image",
        "name": "golden-ami",
        "type": "String",
        "operation": "Create"
    }
}

For information about subscribing to Parameter Store events in EventBridge, see Setting up notifications or trigger actions based on Parameter Store events.