mcpbeat

Cloudformation

itsmostafa/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.

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Install

one command, takes just this skill from the repository 
npx skills add https://github.com/itsmostafa/aws-agent-skills --skill cloudformation

The instruction itself

29 sections, as written by the author

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

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

  PublicSubnet1RouteTableAssociation:
    Type: AWS::EC2::SubnetRouteTableAssociation
    Properties:
      SubnetId: !Ref PublicSubnet1
      RouteTableId: !Ref PublicRouteTable

DynamoDB Table

Resources:
  OrdersTable:
    Type: AWS::DynamoDB::Table
    Properties:
      TableName: !Sub '${AWS::StackName}-orders'
      AttributeDefinitions:
        - AttributeName: PK
          AttributeType: S
        - AttributeName: SK
          AttributeType: S
        - AttributeName: GSI1PK
          AttributeType: S
        - AttributeName: GSI1SK
          AttributeType: S
      KeySchema:
        - AttributeName: PK
          KeyType: HASH
        - AttributeName: SK
          KeyType: RANGE
      GlobalSecondaryIndexes:
        - IndexName: GSI1
          KeySchema:
            - AttributeName: GSI1PK
              KeyType: HASH
            - AttributeName: GSI1SK
              KeyType: RANGE
          Projection:
            ProjectionType: ALL
      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

How to use it

Copy the folder

Take itsmostafa/cloudformation from the repository into ~/.claude/skills for personal use, or into .claude/skills inside a project.

Check the name does not clash

The agent identifies a skill by the name field in its header. Two skills with the same name cannot sit side by side — one of them will be ignored.