How to Use Module from Registry in Terraform: Simple Guide

To use a module from the Terraform Registry, declare a module block in your Terraform configuration with the source set to the registry module address. Then specify any required input variables for that module. Terraform will download and use the module during terraform init and terraform apply.

Syntax

The basic syntax to use a module from the Terraform Registry includes a module block with a unique name, a source attribute pointing to the registry module, and optional input variables.

• module "name": Defines the module block with a unique name.
• source: The registry address of the module, e.g., terraform-aws-modules/vpc/aws.
• version: (Optional) Specifies the module version to use.
• Input variables: Pass values required by the module.

hcl

module "example_module" {
  source  = "terraform-aws-modules/vpc/aws"
  version = "~> 3.0"

  name = "my-vpc"
  cidr = "10.0.0.0/16"
}

Example

This example shows how to use the official AWS VPC module from the Terraform Registry to create a simple VPC with a CIDR block.

hcl

terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 4.0"
    }
  }
}

provider "aws" {
  region = "us-east-1"
}

module "vpc" {
  source  = "terraform-aws-modules/vpc/aws"
  version = "~> 3.0"

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

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

Output

module.vpc.aws_vpc.main: Creating...
module.vpc.aws_vpc.main: Creation complete after 10s [id=vpc-0abcd1234efgh5678]

Apply complete! Resources: 5 added, 0 changed, 0 destroyed.

Common Pitfalls

Common mistakes when using modules from the registry include:

• Not running terraform init after adding a module, so Terraform does not download it.
• Forgetting to specify the source attribute or using an incorrect module address.
• Not providing required input variables, causing errors during plan or apply.
• Using incompatible module versions without specifying version.

hcl

/* Wrong: Missing source attribute */
module "bad_module" {
  name = "test"
}

/* Right: Correct source and inputs */
module "good_module" {
  source = "terraform-aws-modules/vpc/aws"
  version = "~> 3.0"
  name   = "test"
  cidr   = "10.0.0.0/16"
}

Quick Reference

Remember these tips when using Terraform Registry modules:

• Always specify source with the full registry path.
• Use version to lock module versions for stability.
• Run terraform init after adding or changing modules.
• Check module documentation for required inputs.

Key Takeaways

Use a module block with source pointing to the registry module address.

Always run terraform init to download modules before applying.

Specify required input variables as documented by the module.

Lock module versions with version to avoid unexpected changes.

Check for common mistakes like missing source or inputs to prevent errors.