Infrastructure as Code

Guiding Principles

1. Security First: Non-root users, minimal images, secret management
2. Reproducibility: Pin versions, deterministic builds, locked dependencies
3. Modularity: Reusable modules, DRY patterns, clear interfaces
4. State Management: Remote state, locking, backup strategies

Tool Selection

Use Case	Tool
Cloud infrastructure	Terraform
Containers	Docker
Configuration management	Ansible
AWS-native IaC	CloudFormation

Terraform Quick Reference

Essential Commands

terraform init                    # Initialize working directory
terraform plan                    # Preview changes
terraform plan -out=tfplan        # Save plan for apply
terraform apply tfplan            # Apply saved plan
terraform fmt -recursive          # Format all files
terraform validate                # Validate configuration

Critical Patterns

# 1. Pin provider versions
terraform {
  required_version = ">= 1.6.0"
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 5.60"
    }
  }
}

# 2. Use for_each for stability
resource "aws_subnet" "private" {
  for_each = var.private_subnets  # NOT: count
}

# 3. Validate inputs
variable "environment" {
  type = string
  validation {
    condition     = can(regex("^(dev|staging|prod)$", var.environment))
    error_message = "Must be: dev, staging, prod."
  }
}

# 4. Mark sensitive data
variable "db_password" {
  type      = string
  sensitive = true
}

# 5. Lifecycle protection
resource "aws_s3_bucket" "state" {
  lifecycle {
    prevent_destroy = true
  }
}

Docker Quick Reference

Multi-Stage Build

# Build stage
FROM node:20-alpine AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci --only=production
COPY . .
RUN npm run build

# Production stage
FROM node:20-alpine
WORKDIR /app
COPY --from=builder /app/dist ./dist
COPY --from=builder /app/node_modules ./node_modules

USER node
EXPOSE 3000
CMD ["node", "dist/index.js"]

Best Practices

# Pin versions
FROM python:3.12.1-slim-bookworm

# Run as non-root
RUN useradd -m appuser
USER appuser

# Layer optimization
COPY requirements.txt .
RUN pip install -r requirements.txt
COPY . .

# Health check
HEALTHCHECK --interval=30s --timeout=3s \
  CMD curl -f http://localhost:8080/health || exit 1

Naming Conventions

Tool	Convention	Example
Terraform	snake_case	aws_vpc.main
Docker	lowercase, hyphens	my-app:1.0.0
Ansible	snake_case	install_packages
CloudFormation	Hungarian	pEnvironment, rVpc

Security Checklist

• No secrets in code (use vaults/secret managers)
• Non-root containers
• Minimal base images
• Version pinning
• Vulnerability scanning
• State encryption (Terraform)
• Network segmentation

Detailed References

• Terraform: See references/terraform.md
• Docker: See references/docker.md
• Ansible: See references/ansible.md
• Configuration: See references/configuration.md