Attach an IAM role to your existing Amazon EC2 instance

You can now attach or replace an AWS Identity and Access Management (IAM) role to your existing Amazon EC2 instance. IAM roles enable your applications running on EC2 to use temporary security credentials that AWS creates, distributes, and rotates automatically. Using temporary credentials reduces the risk of long-term key compromise. To enable IAM roles for your existing EC2 instances, follow the example described in the AWS Security Blog post.
Quelle: aws.amazon.com