𝑨𝑾𝑺 𝑪𝒍𝒐𝒖𝒅𝑭𝒐𝒓𝒎𝒂𝒕𝒊𝒐𝒏 – 𝑰𝒏𝒇𝒓𝒂𝒔𝒕𝒓𝒖𝒄𝒕𝒖𝒓𝒆 𝒂𝒔 𝑪𝒐𝒅𝒆

What is AWS CloudFormation?

AWS CloudFormation is a service that helps you model and set up your AWS resources so that you can spend less time managing those resources and more time focusing on your applications that run in AWS. You create a template that describes all the AWS resources that you want (like Amazon EC2 instances or Amazon RDS DB instances), and CloudFormation takes care of provisioning and configuring those resources for you. You don't need to individually create and configure AWS resources and figure out what's dependent on what; CloudFormation handles that. The following scenarios demonstrate how CloudFormation can help.

Key concepts

When you use CloudFormation, you work with templates and stacks. You create templates to describe your AWS resources and their properties. Whenever you create a stack, CloudFormation provisions the resources that are described in your template.

Topics

Templates

Stacks

Change sets

Templates

A CloudFormation template is a YAML or JSON formatted text file. You can save these files with any extension, such as .yaml, .json, .template, or .txt. CloudFormation uses these templates as blueprints for building your AWS resources. For example, in a template, you can describe an Amazon EC2 instance, such as the instance type, the AMI ID, block device mappings, and its Amazon EC2 key pair name. Whenever you create a stack, you also specify a template that CloudFormation uses to create whatever you described in the template.

Stacks

When you use CloudFormation, you manage related resources as a single unit called a stack. You create, update, and delete a collection of resources by creating, updating, and deleting stacks. All the resources in a stack are defined by the stack's CloudFormation template. Suppose you created a template that includes an Auto Scaling group, Elastic Load Balancing load balancer, and an Amazon Relational Database Service (Amazon RDS) database instance. To create those resources, you create a stack by submitting the template that you created, and CloudFormation provisions all those resources for you.

Change sets

If you need to make changes to the running resources in a stack, you update the stack. Before making changes to your resources, you can generate a change set, which is a summary of your proposed changes. Change sets allow you to see how your changes might impact your running resources, especially for critical resources, before implementing them.

How CloudFormation works

When you use CloudFormation to create your stack, CloudFormation makes underlying service calls to AWS to provision and configure the resources described in your template. You need permission to create these resources. For example, to create EC2 instances by using CloudFormation, you need permissions to create instances. You manage these permissions with AWS Identity and Access Management (IAM).

The calls that CloudFormation makes are all declared by your template. For example, suppose you have a template that describes an EC2 instance with a t2.micro instance type. When you use that template to create a stack, CloudFormation calls the Amazon EC2 create instance API and specifies the instance type as t2.micro. The following diagram summarizes the CloudFormation workflow for creating stacks.