Using IAM Roles and Temporary Credentials to Grant EC2 Instances Access

The article explains why servers and applications should use IAM roles rather than long-lived user credentials, since roles issue temporary access that is rotated automatically. It describes the two parts of a role: a trust policy that defines which service may assume it, and a permissions policy that defines what it can do. Attaching a role to an EC2 instance through an instance profile lets software retrieve short-lived credentials from the instance metadata service, with nothing stored on disk. The author walks through a hands-on test using a least-privilege S3 read policy, verifying access with the AWS CLI and confirming denied access to other buckets. Common mistakes are also highlighted, such as embedding access keys in code, overly broad trust policies, and attaching administrator permissions to roles.