How to provide AWS credentials to EC2 instances

Difficulty: 6/10

IAM roles, Instance metadata service, Credential rotation

Using IAM Roles for EC2

The most secure way to provide credentials to an EC2 instance is by using IAM Roles. You should never hardcode AWS Access Keys or Secret Keys within your application code or configuration files. Instead, you attach an IAM Role to the instance, and the AWS SDKs automatically fetch temporary credentials from the Instance Metadata Service (IMDS).

Retrieving Temporary Credentials via CLI

Benefits of IAM Roles

1
Automatic credential rotation performed by AWS.
2
No long-term secrets stored on the instance disk.
3
Easily managed via IAM policies and central identity management.

Scenario Questions

0-2 years experience

1You need your application on an EC2 instance to read objects from an S3 bucket. How would you provide the necessary AWS credentials without hard‑coding keys?
2If you launch an EC2 instance from the console and forget to attach an IAM role, what will happen when the app tries to call AWS APIs, and how can you fix it?
3Explain how you would retrieve temporary credentials from the instance metadata service inside a startup script.

Follow-up Questions

What would you monitor to detect credential misuse?
How would you automate the attachment of the correct IAM role during instance launch?
Which controls would you put in place to protect credentials if the instance is compromised?