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AWS CLI and SDK

Updated Jul 26, 2020 ·
NOTES

This is not an exhaustive documentation of all the existing AWS Services. These are summarized notes that I used for the AWS Certifications.

To see the complete documentation, please go to: AWS documentation

AWS CLI (Command Line Interface)​

Add user credentials locally using this command:

aws configure

If you are using multiple AWS accounts, you can add custom profiles with seperate credentials using this command:

aws configure --profile {my-other-aws-account}

If you you'd like to execute commands on a specific profile, example:

aws s3 ls --profile {my-other-aws-account}

``

If you don't specify the aws profile, the commands will be executed to your default profile

AWS CLI on EC2​

  • IAM roles can be attached to EC2 instances
  • IAM roles can come with a policy authorizing exactly what the EC2 instance should be able to do. This is the best practice.
  • EC2 Instances can then use these profiles automatically without any additional configurations

CLI STS Decode Errors​

  • When you run API calls and they fail, you can get a long, encoded error message code.

  • This error can be decoded using STS.

  • Run the command:

    aws sts decode-authorization-message --encoded-message {encoded_message_code}

  • Your IAM user must have the correct permissions to use this command by adding the STS service to your policy.

SDK (Software Development Kit)​

If you want to perform actions on AWS directly from your application's code without using a CLI, you can use an SDK.

Official SDKs:

  • Java
  • .NET
  • Node.js
  • PHP
  • Python
  • Ruby
  • C++

Key points​

  • AWS SDK are required when coding against AWS Services such as DynamoDB.
  • Fact: AWS CLI uses the Python SDK (boto3).
  • The exam expects you to know when you should use an SDK.
  • If you don’t specify or configure a default region, then us-east-1 will be chosen by default.

SDK Credentials Security​

  • It’s recommend to use the default credential provider chain.
  • The default credential provider chain works seamlessly with:
    • AWS credentials at ~/.aws/credentials (only on our computers or on premise).
    • Instance Profile Credentials using IAM Roles (for EC2 machines, etc.).
  • Environment variables (AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY).
  • Overall, NEVER EVER STORE AWS CREDENTIALS IN YOUR CODE.
  • Use IAM Roles if working from within AWS Services to inherit credentials.

Exponential Backoff​

  • Any API that fails because of too many calls needs to be retried with Exponential Backoff.

  • These apply to rate limited API.

  • Retry mechanism is included in SDK API calls.