Terraform Tutorial — Terraform Registry Modules

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The Terraform Registry hosts thousands of pre-built modules. Instead of writing everything from scratch, you can use community and HashiCorp-verified modules.

Finding Modules

  1. Browse registry.terraform.io/browse/modules
  2. Search by provider or keyword (e.g., “aws vpc”)
  3. Look for the Verified badge — maintained by HashiCorp or the provider
Module Source Purpose
VPC terraform-aws-modules/vpc/aws Complete VPC with subnets, NAT, routes
EKS terraform-aws-modules/eks/aws Kubernetes cluster on AWS
S3 Bucket terraform-aws-modules/s3-bucket/aws S3 with policies and lifecycle rules
Security Group terraform-aws-modules/security-group/aws Flexible SG rules
RDS terraform-aws-modules/rds/aws Managed database

Using a Registry Module

module "vpc" {
  source  = "terraform-aws-modules/vpc/aws"
  version = "5.4.0"    # ← always pin the version

  name = "production"
  cidr = "10.0.0.0/16"

  azs             = ["us-east-1a", "us-east-1b", "us-east-1c"]
  private_subnets = ["10.0.1.0/24", "10.0.2.0/24", "10.0.3.0/24"]
  public_subnets  = ["10.0.101.0/24", "10.0.102.0/24", "10.0.103.0/24"]

  enable_nat_gateway = true
  single_nat_gateway = true

  tags = {
    Environment = "production"
    Terraform   = "true"
  }
}

Version Constraints

Constraint Meaning
"5.4.0" Exact version
"~> 5.4" >= 5.4.0, < 5.5.0 (patch updates only)
">= 5.0" Any version 5.0 or newer
">= 5.0, < 6.0" Major version 5 only

💡 Tip: Use ~> for production. It allows patch updates (bug fixes) but prevents breaking changes.

Local vs Registry Modules

Aspect Local Module Registry Module
Source "./modules/vpc" "terraform-aws-modules/vpc/aws"
Versioning Git tags / manual Built-in version attribute
Maintenance Your team Community / HashiCorp
Customization Full control Limited to exposed variables
Trust You wrote it Review the code first

What’s Next?

Practice building and using modules with the exercises.

← Module Inputs and Outputs Practice Exercises →

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