Terraform Tutorial — Calling a Module

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You call a module using the module block in your root configuration. The source argument tells Terraform where to find the module.

Calling a Local Module

module "vpc" {
  source = "./modules/vpc"

  name               = "myapp"
  cidr_block         = "10.0.0.0/16"
  public_subnets     = ["10.0.1.0/24", "10.0.2.0/24"]
  availability_zones = ["us-east-1a", "us-east-1b"]

  tags = {
    Environment = "dev"
    Project     = "myapp"
  }
}

Calling a Registry Module

module "vpc" {
  source  = "terraform-aws-modules/vpc/aws"
  version = "5.4.0"

  name = "myapp-vpc"
  cidr = "10.0.0.0/16"

  azs             = ["us-east-1a", "us-east-1b"]
  public_subnets  = ["10.0.1.0/24", "10.0.2.0/24"]
  private_subnets = ["10.0.10.0/24", "10.0.20.0/24"]

  enable_nat_gateway = true
  single_nat_gateway = true
}

Calling a Git Module

module "vpc" {
  source = "git::https://github.com/myorg/terraform-modules.git//vpc?ref=v1.2.0"

  name       = "myapp"
  cidr_block = "10.0.0.0/16"
}

Module Block Arguments

Argument Required Purpose
source ✅ Yes Where to find the module
version Recommended Pin a specific version (registry only)
Variables Depends Each variable the module declares
providers Optional Pass specific provider configurations
depends_on Optional Explicit dependency on other resources
count Optional Create zero or more instances
for_each Optional Create instances from a map/set

Re-run init After Adding a Module

When you add a new module, run terraform init to download it:

$ terraform init
Initializing modules...
- vpc in ./modules/vpc

Initializing provider plugins...

Multiple Instances of a Module

Use the same module with different inputs:

module "vpc_dev" {
  source     = "./modules/vpc"
  name       = "dev"
  cidr_block = "10.0.0.0/16"
  availability_zones = ["us-east-1a", "us-east-1b"]
}

module "vpc_prod" {
  source     = "./modules/vpc"
  name       = "prod"
  cidr_block = "10.1.0.0/16"
  availability_zones = ["us-east-1a", "us-east-1b", "us-east-1c"]
}

What’s Next?

Let’s dive deeper into passing inputs and receiving outputs from modules.

← Module Structure Module Inputs and Outputs →

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