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What is AWS ARN?

Published in AWS Fundamentals 3 mins read

An Amazon Resource Name (ARN) is a unique identifier for every AWS resource. It's like a social security number, but for your AWS resources, ensuring each one can be distinctly recognized within the AWS ecosystem.

Understanding ARNs

ARNs are crucial for managing permissions and access control in AWS. When you grant permissions to users, roles, or services, you typically specify the resources they can access using ARNs. This allows for fine-grained control over your AWS environment.

ARN Structure

ARNs follow a standardized format that includes several components:

arn:partition:service:region:account-id:resource
arn:partition:service:region:account-id:resource-type/resource-id
arn:partition:service:region:account-id:resource-type:resource-id

Let's break down each part:

  • arn: This is a constant and always the prefix for an ARN.
  • partition: This indicates the AWS partition the resource belongs to (e.g., aws, aws-cn, aws-us-gov).
  • service: This specifies the AWS service (e.g., s3, ec2, lambda).
  • region: This indicates the AWS Region where the resource resides (e.g., us-west-2, eu-central-1). For some global services like IAM, this field might be empty.
  • account-id: This is the 12-digit AWS account ID, without hyphens.
  • resource: This is the service-specific identifier of the resource. It can take different forms depending on the service and resource type. It can be a resource name, a path, or a combination of resource types and IDs.

Examples of ARNs

Here are some examples of ARNs for different AWS resources:

  • S3 Bucket: arn:aws:s3:::my-bucket
  • EC2 Instance: arn:aws:ec2:us-west-2:123456789012:instance/i-0abcdef1234567890
  • IAM User: arn:aws:iam::123456789012:user/johndoe
  • Lambda Function: arn:aws:lambda:us-east-1:123456789012:function:my-function
  • DynamoDB Table: arn:aws:dynamodb:us-west-2:123456789012:table/my-table

Importance of ARNs

  • Uniqueness: ARNs guarantee that each AWS resource has a unique identifier across all AWS accounts and Regions.
  • Access Control: ARNs are used in IAM policies to grant or deny permissions to specific resources.
  • Resource Identification: ARNs allow you to unambiguously identify resources when configuring AWS services and applications.
  • Automation: ARNs are critical for automating infrastructure management tasks using tools like AWS CloudFormation, AWS CLI, and AWS SDKs.

In summary, an AWS ARN is a fundamental concept for managing and securing your AWS resources by providing a consistent and unique way to identify them. Understanding ARNs is essential for effective AWS administration and security best practices.

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