Introduction to AWS CloudFormation

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What is CloudFormation?

AWS CloudFormation is a service that lets you model and provision AWS resources in an automated and repeatable way.

Basic principle

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Key concepts

1. Template

A template is a YAML or JSON file that describes the AWS resources to create.

AWSTemplateFormatVersion: '2010-09-09'
Description: Mon premier template CloudFormation

Resources:
  MonBucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName: mon-bucket-unique-12345

2. Stack

A stack is a collection of AWS resources managed as a single unit.

3. Change Set

A change set lets you preview modifications before applying them.

4. Stack Events

Events track all operations on the stack.

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CloudFormation vs Terraform

Aspect	CloudFormation	Terraform
Provider	AWS only	Multi-cloud
Language	YAML/JSON	HCL
State	Managed by AWS	Local or remote file
Cost	Free	Free (Open Source)
Drift Detection	Built-in	Limited
Rollback	Automatic	Manual
Modules	Nested Stacks	Native modules

When to use CloudFormation?

• 100% AWS infrastructure
• Need for automatic rollback
• Team already familiar with AWS
• Integration with AWS Organizations

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CloudFormation workflow

Workflow steps

1. Write: Create the YAML/JSON template
2. Validate: Check the syntax
3. Create/Update: Deploy the stack
4. Monitor: Check the events
5. Maintain: Manage the lifecycle

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First template

Let's create a simple S3 bucket:

AWSTemplateFormatVersion: '2010-09-09'
Description: Création d'un bucket S3 simple

Resources:
  MyS3Bucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName: !Sub 'my-first-bucket-${AWS::AccountId}'
      Tags:
        - Key: Environment
          Value: Development
        - Key: ManagedBy
          Value: CloudFormation

Deployment via CLI

# Valider le template
aws cloudformation validate-template \
    --template-body file://template.yaml

# Créer la stack
aws cloudformation create-stack \
    --stack-name my-first-stack \
    --template-body file://template.yaml

# Vérifier le statut
aws cloudformation describe-stacks \
    --stack-name my-first-stack

# Voir les events
aws cloudformation describe-stack-events \
    --stack-name my-first-stack

Deployment via Console

1. Open the CloudFormation console
2. Click Create stack
3. Upload the template
4. Name the stack
5. Configure the options
6. Review and create

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Stack states

State	Description
CREATE_IN_PROGRESS	Creation in progress
CREATE_COMPLETE	Creation succeeded
CREATE_FAILED	Creation failed
UPDATE_IN_PROGRESS	Update in progress
DELETE_IN_PROGRESS	Deletion in progress
ROLLBACK_IN_PROGRESS	Rollback in progress

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Regions and availability

CloudFormation is available in all AWS regions. Each stack is created in a specific region.

# Créer dans une région spécifique
aws cloudformation create-stack \
    --stack-name my-stack \
    --template-body file://template.yaml \
    --region eu-west-1

# Lister les stacks d'une région
aws cloudformation list-stacks \
    --region eu-west-1 \
    --stack-status-filter CREATE_COMPLETE UPDATE_COMPLETE

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Limits and quotas

Limit	Value
Max template size (S3)	1 MB
Max template size (direct)	51,200 bytes
Resources per stack	500
Stacks per account/region	2000
Parameters per template	200
Outputs per template	200
Mappings per template	200

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Essential CLI commands

# Créer une stack
aws cloudformation create-stack \
    --stack-name NAME \
    --template-body file://template.yaml

# Mettre à jour une stack
aws cloudformation update-stack \
    --stack-name NAME \
    --template-body file://template.yaml

# Supprimer une stack
aws cloudformation delete-stack \
    --stack-name NAME

# Lister les stacks
aws cloudformation list-stacks

# Décrire une stack
aws cloudformation describe-stacks \
    --stack-name NAME

# Créer un change set
aws cloudformation create-change-set \
    --stack-name NAME \
    --change-set-name my-changes \
    --template-body file://template.yaml

# Exécuter un change set
aws cloudformation execute-change-set \
    --stack-name NAME \
    --change-set-name my-changes

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Summary

• CloudFormation is AWS's native IaC service
• Templates describe the infrastructure
• Stacks group resources together
• Change sets allow you to preview
• Rollback is automatic on error

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