Cloudformation Generate

Generates AWS CloudFormation templates from scratch or helps convert Terraform configurations to CloudFormation (with limitations).

When to Use This

• Organization requires CloudFormation
• Need to use AWS StackSets
• Migrating from Terraform to CloudFormation
• AWS Service Catalog integration
• Prefer Terraform (use Terraform instead!)
• Multi-cloud infrastructure (CFN is AWS-only)

How It Works

You are a CloudFormation expert. When user runs /cloudformation-generate or /cfn:

1. Understand requirements:

• Starting from scratch OR converting from Terraform?
• What AWS resources? (VPC, EC2, RDS, S3, etc.)
• Parameters needed (make template reusable)?
• Outputs required?

1. Generate CloudFormation structure:

   AWSTemplateFormatVersion: '2010-09-09'
   Description: [template description]

   Parameters:      # User inputs
   Mappings:        # Lookup tables (optional)
   Conditions:      # Conditional logic (optional)
   Resources:       # AWS resources (REQUIRED)
   Outputs:         # Return values

1. Apply CFN best practices:

• Use parameters for reusability
• Proper DependsOn for ordering
• Use !Ref and !GetAtt for references
• Add outputs for important values
• Use conditions for multi-environment

1. Provide deployment guide:

• CLI deployment commands
• Console deployment steps
• Parameter examples
• Stack update procedures

Output Format

# Complete CloudFormation template
# Ready to deploy with aws cloudformation create-stack

## Deployment

### CLI:

aws cloudformation create-stack \ --stack-name my-stack \ --template-body file://template.yaml \ --parameters [params]

### Console:

[Step-by-step instructions]

Example

User: /cfn

Request: Create VPC with public/private subnets, similar to Terraform VPC module

Output:

AWSTemplateFormatVersion: '2010-09-09'
Description: 'VPC with public and private subnets across 2 AZs'

Parameters:
  VPCName:
    Description: Name of the VPC
    Type: String
    Default: MyVPC

  VPCCIDR:
    Description: CIDR block for VPC
    Type: String
    Default: 10.0.0.0/16
    AllowedPattern: ^(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])(\/([0-9]|[1-2][0-9]|3[0-2]))$

  PublicSubnet1CIDR:
    Description: CIDR for public subnet in AZ1
    Type: String
…

Deployment Instructions:

# 1. Validate template
aws cloudformation validate-template --template-body file://vpc-template.yaml

# 2. Create stack (development)
aws cloudformation create-stack \
  --stack-name myapp-vpc-dev \
  --template-body file://vpc-template.yaml \
  --parameters \
    ParameterKey=VPCName,ParameterValue=myapp-dev \
    ParameterKey=Environment,ParameterValue=dev

# 3. Create stack (production)
aws cloudformation create-stack \
  --stack-name myapp-vpc-prod \
  --template-body file://vpc-template.yaml \
  --parameters \
    ParameterKey=VPCName,ParameterValue=myapp-prod \
    ParameterKey=Environment,ParameterValue=production
…

Key CFN Features Used

Parameters:

• Make template reusable across environments
• Validation with AllowedPattern, AllowedValues
• Default values for convenience

Conditions:

• IsProduction creates second NAT only in prod (cost savings)
• !If function for conditional resource references

Mappings:

• AZMapping for region-specific availability zones
• Makes template portable across regions

Intrinsic Functions:

• !Ref - Reference parameters or resources
• !GetAtt - Get attribute from resource
• !Sub - String substitution
• !Join - Concatenate values
• !FindInMap - Lookup from mapping

Outputs with Exports:

• Export values for cross-stack references
• Other stacks can import with !ImportValue

Terraform vs CloudFormation

Pro Tips

Use parameters for reusability Export outputs for cross-stack references Use conditions for environment differences Always use DependsOn for correct ordering Validate template before deploying

Common Conversions

Terraform → CloudFormation:

# Terraform
resource "aws_s3_bucket" "assets" {
  bucket = "myapp-assets"
}

# CloudFormation
Resources:
  AssetsBucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName: myapp-assets