Aws Cloudformation

AWS CloudFormation infrastructure as code for stack management. Use when writing templates, deploying stacks, managing drift, troubleshooting deployments, or organizing infrastructure with nested stacks.

Third-party community skill

This skill is reviewed through Azure/git-ape PRs and maintained by its listed author. It is not bundled or activated with core. See the Skill Registry and use /git-ape-skills install aws-cloudformation for explicit project or personal installation. Review is not a guarantee of safety.

Details

Property	Value
Skill Directory	.github/community-skills/aws-cloudformation/
Author	dawright22
Maturity	experimental
Available with Core	❌ No — explicit installation required
Usage	/aws-cloudformation Template section, resource type, or operation to look up (e.g. 'Parameters section', 'Lambda function resource', 'change set', 'drift detection')

Documentation

AWS CloudFormation

AWS CloudFormation provisions and manages AWS resources using templates. Define infrastructure as code, version control it, and deploy consistently across environments.

Table of Contents

• Core Concepts
• Common Patterns
• CLI Reference
• Best Practices
• Troubleshooting
• References

Core Concepts

Templates

JSON or YAML files defining AWS resources. Key sections:

• Parameters: Input values
• Mappings: Static lookup tables
• Conditions: Conditional resource creation
• Resources: AWS resources (required)
• Outputs: Return values

Stacks

Collection of resources managed as a single unit. Created from templates.

Change Sets

Preview changes before executing updates.

Stack Sets

Deploy stacks across multiple accounts and regions.

Common Patterns

Basic Template Structure

AWSTemplateFormatVersion: '2010-09-09'
Description: My infrastructure template

Parameters:
  Environment:
    Type: String
    AllowedValues: [dev, staging, prod]
    Default: dev

Mappings:
  EnvironmentConfig:
    dev:
      InstanceType: t3.micro
    prod:
      InstanceType: t3.large

Conditions:
  IsProd: !Equals [!Ref Environment, prod]

Resources:
  MyBucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName: !Sub 'my-app-${Environment}-${AWS::AccountId}'
      VersioningConfiguration:
        Status: !If [IsProd, Enabled, Suspended]

Outputs:
  BucketName:
    Description: S3 bucket name
    Value: !Ref MyBucket
    Export:
      Name: !Sub '${AWS::StackName}-BucketName'

Deploy a Stack

AWS CLI:

# Create stack
aws cloudformation create-stack \
  --stack-name my-stack \
  --template-body file://template.yaml \
  --parameters ParameterKey=Environment,ParameterValue=prod \
  --capabilities CAPABILITY_IAM

# Wait for completion
aws cloudformation wait stack-create-complete --stack-name my-stack

# Update stack
aws cloudformation update-stack \
  --stack-name my-stack \
  --template-body file://template.yaml \
  --parameters ParameterKey=Environment,ParameterValue=prod

# Delete stack
aws cloudformation delete-stack --stack-name my-stack

Use Change Sets

# Create change set
aws cloudformation create-change-set \
  --stack-name my-stack \
  --change-set-name my-changes \
  --template-body file://template.yaml \
  --parameters ParameterKey=Environment,ParameterValue=prod

# Describe changes
aws cloudformation describe-change-set \
  --stack-name my-stack \
  --change-set-name my-changes

# Execute change set
aws cloudformation execute-change-set \
  --stack-name my-stack \
  --change-set-name my-changes

Lambda Function in CloudFormation

Resources:
  LambdaFunction:
    Type: AWS::Lambda::Function
    Properties:
      FunctionName: !Sub '${AWS::StackName}-function'
      Runtime: python3.12
      Handler: index.handler
      Role: !GetAtt LambdaRole.Arn
      Code:
        ZipFile: |
          def handler(event, context):
              return {'statusCode': 200, 'body': 'Hello'}
      Environment:
        Variables:
          ENVIRONMENT: !Ref Environment

  LambdaRole:
    Type: AWS::IAM::Role
    Properties:
      AssumeRolePolicyDocument:
        Version: '2012-10-17'
        Statement:
          - Effect: Allow
            Principal:
              Service: lambda.amazonaws.com
            Action: sts:AssumeRole
      ManagedPolicyArns:
        - arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole

VPC with Subnets

Resources:
  VPC:
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: 10.0.0.0/16
      EnableDnsHostnames: true
      Tags:
        - Key: Name
          Value: !Sub '${AWS::StackName}-vpc'

  PublicSubnet1:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      AvailabilityZone: !Select [0, !GetAZs '']
      CidrBlock: 10.0.1.0/24
      MapPublicIpOnLaunch: true

  PrivateSubnet1:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      AvailabilityZone: !Select [0, !GetAZs '']
      CidrBlock: 10.0.10.0/24

  InternetGateway:
    Type: AWS::EC2::InternetGateway

  AttachGateway:
    Type: AWS::EC2::VPCGatewayAttachment
    Properties:
      VpcId: !Ref VPC
      InternetGatewayId: !Ref InternetGateway

  PublicRouteTable:
    Type: AWS::EC2::RouteTable
    Properties:
      VpcId: !Ref VPC

  PublicRoute:
    Type: AWS::EC2::Route
    DependsOn: AttachGateway
    Properties:
      RouteTableId: !Ref PublicRouteTable
      DestinationCidrBlock: 0.0.0.0/0
      GatewayId: !Ref InternetGateway

DynamoDB Table

Resources:
  OrdersTable:
    Type: AWS::DynamoDB::Table
    Properties:
      TableName: !Sub '${AWS::StackName}-orders'
      AttributeDefinitions:
        - AttributeName: PK
          AttributeType: S
        - AttributeName: SK
          AttributeType: S
      KeySchema:
        - AttributeName: PK
          KeyType: HASH
        - AttributeName: SK
          KeyType: RANGE
      BillingMode: PAY_PER_REQUEST
      PointInTimeRecoverySpecification:
        PointInTimeRecoveryEnabled: true

CLI Reference

Stack Operations

Command	Description
aws cloudformation create-stack	Create stack
aws cloudformation update-stack	Update stack
aws cloudformation delete-stack	Delete stack
aws cloudformation describe-stacks	Get stack info
aws cloudformation list-stacks	List stacks
aws cloudformation describe-stack-events	Get events
aws cloudformation describe-stack-resources	Get resources

Change Sets

Command	Description
aws cloudformation create-change-set	Create change set
aws cloudformation describe-change-set	View changes
aws cloudformation execute-change-set	Apply changes
aws cloudformation delete-change-set	Delete change set

Template

Command	Description
aws cloudformation validate-template	Validate template
aws cloudformation get-template	Get stack template
aws cloudformation get-template-summary	Get template info

Best Practices

Template Design

• Use parameters for environment-specific values
• Use mappings for static lookup tables
• Use conditions for optional resources
• Export outputs for cross-stack references
• Add descriptions to parameters and outputs

Security

• Use IAM roles instead of access keys
• Enable termination protection for production
• Use stack policies to protect resources
• Never hardcode secrets — use Secrets Manager

# Enable termination protection
aws cloudformation update-termination-protection \
  --stack-name my-stack \
  --enable-termination-protection

Organization

• Use nested stacks for complex infrastructure
• Create reusable modules
• Version control templates
• Use consistent naming conventions

Reliability

• Use DependsOn for explicit dependencies
• Configure creation policies for instances
• Use update policies for Auto Scaling groups
• Implement rollback triggers

Troubleshooting

Stack Creation Failed

# Get failure reason
aws cloudformation describe-stack-events \
  --stack-name my-stack \
  --query 'StackEvents[?ResourceStatus==`CREATE_FAILED`]'

# Common causes:
# - IAM permissions
# - Resource limits
# - Invalid property values
# - Dependency failures

Stack Stuck in DELETE_FAILED

# Identify resources that couldn't be deleted
aws cloudformation describe-stack-resources \
  --stack-name my-stack \
  --query 'StackResources[?ResourceStatus==`DELETE_FAILED`]'

# Retry with resources to skip
aws cloudformation delete-stack \
  --stack-name my-stack \
  --retain-resources ResourceLogicalId1 ResourceLogicalId2

Drift Detection

# Detect drift
aws cloudformation detect-stack-drift --stack-name my-stack

# Check drift status
aws cloudformation describe-stack-drift-detection-status \
  --stack-drift-detection-id abc123

# View drifted resources
aws cloudformation describe-stack-resource-drifts \
  --stack-name my-stack

Rollback Failed

# Continue update rollback
aws cloudformation continue-update-rollback \
  --stack-name my-stack \
  --resources-to-skip ResourceLogicalId1

References

• CloudFormation User Guide
• CloudFormation API Reference
• CloudFormation CLI Reference
• Resource and Property Reference