Exploring `aws cli another account s3 ls`

The AWS Command Line Interface (AWS CLI) is a powerful tool that allows developers and system administrators to interact with various AWS services directly from the command line. One common use - case is listing the contents of an Amazon S3 bucket (s3 ls). However, when you need to access an S3 bucket in another AWS account, it involves additional steps and concepts. This blog post will delve into the details of using aws cli another account s3 ls, explaining core concepts, typical usage scenarios, common practices, and best practices.

Table of Contents#

  1. Core Concepts
  2. Typical Usage Scenarios
  3. Common Practice
  4. Best Practices
  5. Conclusion
  6. FAQ
  7. References

Article#

Core Concepts#

AWS Identity and Access Management (IAM)#

IAM is a service that enables you to manage access to AWS services and resources. To list the contents of an S3 bucket in another account, you need appropriate IAM permissions. There are two main ways to achieve this:

  • Cross - Account Role: The account that owns the S3 bucket (the target account) creates an IAM role with permissions to access the S3 bucket. The user or role in the source account can then assume this role to access the S3 bucket.
  • Bucket Policy: The bucket owner can attach a bucket policy to the S3 bucket that allows specific principals (users, roles, or accounts) from other accounts to access the bucket.

AWS STS (Security Token Service)#

AWS STS is used to request temporary, limited - privilege credentials. When you assume a cross - account role, STS provides you with temporary access keys (access key ID, secret access key, and a session token) that you can use to authenticate your AWS CLI requests.

Typical Usage Scenarios#

Data Sharing between Departments#

In a large organization, different departments may have their own AWS accounts. For example, the data science department may need to access data stored in an S3 bucket owned by the marketing department. By using aws cli another account s3 ls, data scientists can list the available datasets in the marketing department's S3 bucket.

Third - Party Data Access#

A company may work with third - party vendors who store data in their own AWS accounts. The company can use the AWS CLI to access and list the contents of the vendor's S3 buckets, given the appropriate permissions.

Common Practice#

Step 1: Create a Cross - Account Role in the Target Account#

  1. Log in to the AWS Management Console of the target account (the account that owns the S3 bucket).
  2. Navigate to the IAM service and create a new role.
  3. Select "Another AWS account" as the trusted entity type.
  4. Enter the account ID of the source account.
  5. Attach a policy that allows s3:ListBucket permissions for the specific S3 bucket.

Step 2: Configure the Source Account to Assume the Role#

  1. In the source account, configure the AWS CLI with your own AWS credentials.
  2. Use the aws sts assume - role command to assume the cross - account role. For example:
aws sts assume - role --role - arn "arn:aws:iam::TARGET_ACCOUNT_ID:role/ROLE_NAME" --role - session - name "MySession"
  1. This command will return temporary credentials. Set these credentials as environment variables:
export AWS_ACCESS_KEY_ID=ACCESS_KEY_FROM_ASSUME_ROLE
export AWS_SECRET_ACCESS_KEY=SECRET_ACCESS_KEY_FROM_ASSUME_ROLE
export AWS_SESSION_TOKEN=SESSION_TOKEN_FROM_ASSUME_ROLE

Step 3: List the S3 Bucket Contents#

Now you can use the aws s3 ls command to list the contents of the S3 bucket in the target account:

aws s3 ls s3://TARGET_BUCKET_NAME

Best Practices#

Use IAM Roles Instead of Long - Term Credentials#

Using IAM roles and temporary credentials is more secure than using long - term access keys. Temporary credentials have a limited lifespan, reducing the risk of credential compromise.

Least Privilege Principle#

When creating IAM policies, follow the least privilege principle. Only grant the minimum permissions required to perform the s3 ls operation. For example, if you only need to list the bucket contents, don't grant full S3 access.

Monitor and Audit#

Regularly monitor and audit the usage of cross - account access. AWS CloudTrail can be used to log all API calls, including those related to assuming roles and accessing S3 buckets.

Conclusion#

Using aws cli another account s3 ls allows you to access and list the contents of S3 buckets in other AWS accounts. By understanding core concepts such as IAM and STS, and following common practices and best practices, you can securely and efficiently perform this operation. This functionality is particularly useful in scenarios where data needs to be shared between different accounts within an organization or with external partners.

FAQ#

Q: Can I use aws s3 ls without assuming a role if the bucket policy allows access?#

A: Yes, if the bucket policy directly allows the user or role in the source account to access the bucket, you can use aws s3 ls with your regular AWS credentials.

Q: How long do the temporary credentials obtained from aws sts assume - role last?#

A: By default, the temporary credentials are valid for 1 hour. However, you can specify a different duration (up to 12 hours) when using the --duration - seconds parameter in the aws sts assume - role command.

Q: What if I get an "Access Denied" error when running aws s3 ls?#

A: Check the IAM policy attached to the cross - account role. Make sure it has the necessary s3:ListBucket permissions. Also, verify that the temporary credentials are correctly set as environment variables.

References#

2025-10