Terraform Tutorial — Modules Practice Exercises

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Practice creating and using Terraform modules.

Exercise 1: Module Structure

Task: Create the file structure for a module called s3-bucket that creates an S3 bucket with versioning and tagging. List the files and their purpose.

Answer 
modules/s3-bucket/
├── main.tf          ← S3 bucket resource + versioning
├── variables.tf     ← bucket_name, environment, tags
├── outputs.tf       ← bucket_id, bucket_arn, bucket_domain
├── versions.tf      ← Terraform and AWS provider constraints
└── README.md        ← Usage documentation

Exercise 2: Write a Module

Task: Write variables.tf and outputs.tf for an S3 bucket module that accepts bucket_name (required) and environment (default: “dev”), and outputs the bucket ARN.

Answer 
# modules/s3-bucket/variables.tf
variable "bucket_name" {
  type        = string
  description = "Name of the S3 bucket"
}

variable "environment" {
  type        = string
  default     = "dev"
  description = "Deployment environment"
}

# modules/s3-bucket/outputs.tf
output "bucket_arn" {
  value       = aws_s3_bucket.this.arn
  description = "ARN of the S3 bucket"
}

output "bucket_id" {
  value       = aws_s3_bucket.this.id
  description = "Name/ID of the S3 bucket"
}

Exercise 3: Call a Module

Task: Write the root module code that calls the s3-bucket module twice — once for a “logs” bucket and once for an “assets” bucket.

Answer 
module "logs_bucket" {
  source      = "./modules/s3-bucket"
  bucket_name = "myapp-logs-${var.environment}"
  environment = var.environment
}

module "assets_bucket" {
  source      = "./modules/s3-bucket"
  bucket_name = "myapp-assets-${var.environment}"
  environment = var.environment
}

output "logs_bucket_arn" {
  value = module.logs_bucket.bucket_arn
}

output "assets_bucket_arn" {
  value = module.assets_bucket.bucket_arn
}

Chapter Summary

In this chapter, you learned:

  • Modules eliminate copy-paste and enforce consistency
  • Standard module structure: main.tf, variables.tf, outputs.tf, versions.tf
  • Call modules with the module {} block and source argument
  • Modules communicate through inputs (variables) and outputs
  • The Terraform Registry has thousands of pre-built modules
  • Always pin versions with version = "~> X.Y"
  • Module sources: local paths, Git repos, S3 buckets, registry

Next up: Workspaces — managing multiple environments with isolated state.

← Terraform Registry Modules Workspaces →

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