An introduction to Amazon EC2 credentials When you assign an Identity and Access Management (IAM) role to an Amazon Elastic Compute Cloud (EC2) instance, the short-term credentials for the role are made available via a web service known as the Instance Metadata Service (IMDS). The IMDS provides an HTTP endpoint for retrieving instance metadata such as the instance IP address, AWS Region the instance is running in, the Amazon Machine Image used to launch the instance, and the access key, secre...