Why modules enable reusability in Terraform - See It in Action

Why modules enable reusability

📖 Scenario: You are managing cloud infrastructure using Terraform. You want to create reusable code blocks to deploy virtual machines with consistent settings across different projects.

🎯 Goal: Build a Terraform module for a virtual machine and reuse it twice with different names and IP addresses.

📋 What You'll Learn

Create a Terraform module with variables for VM name and IP address

Use the module twice in the main configuration with different inputs

Output the VM names from the module instances

💡 Why This Matters

🌍 Real World

Cloud engineers use Terraform modules to reuse infrastructure code for similar resources across projects, saving time and reducing errors.

💼 Career

Understanding modules is essential for infrastructure as code roles, enabling scalable and maintainable cloud deployments.

1

Create a Terraform module with variables

Create a Terraform module folder named vm_module. Inside it, create a file main.tf that defines a resource aws_instance with the name set to the variable vm_name and private IP set to the variable vm_ip. Also create a variables.tf file defining the variables vm_name and vm_ip as strings.

Terraform

# Your code here to create vm_module/main.tf and vm_module/variables.tf with variables vm_name and vm_ip

Need a hint?

Define variables in variables.tf and use them in main.tf inside the module folder.

2

Add module usage in main Terraform configuration

In the root Terraform configuration, create a file main.tf. Add two module blocks named vm1 and vm2 that use the vm_module source. Set vm_name to "web-server-1" and vm_ip to "10.0.1.10" for vm1. Set vm_name to "web-server-2" and vm_ip to "10.0.1.11" for vm2.

Terraform

variable "vm_name" {
  type = string
}

variable "vm_ip" {
  type = string
}

resource "aws_instance" "vm" {
  ami           = "ami-12345678"
  instance_type = "t2.micro"
  private_ip    = var.vm_ip
  tags = {
    Name = var.vm_name
  }
}

# Add two module blocks named vm1 and vm2 using vm_module source
# Your code here

Need a hint?

Use module "name" { source = "./vm_module" ... } blocks to reuse the module with different inputs.

3

Add outputs in the module

Inside the vm_module folder, create a file outputs.tf. Add an output named vm_name_output that outputs the tag Name of the aws_instance.vm resource.

Terraform

variable "vm_name" {
  type = string
}

variable "vm_ip" {
  type = string
}

resource "aws_instance" "vm" {
  ami           = "ami-12345678"
  instance_type = "t2.micro"
  private_ip    = var.vm_ip
  tags = {
    Name = var.vm_name
  }
}

# Add output vm_name_output in vm_module/outputs.tf
# Your code here

Need a hint?

Outputs allow you to expose values from modules. Use output "name" { value = ... }.

4

Output module instance names in root configuration

In the root main.tf, add two outputs named vm1_name and vm2_name. Set their values to the outputs vm_name_output from the modules vm1 and vm2 respectively.

Terraform

variable "vm_name" {
  type = string
}

variable "vm_ip" {
  type = string
}

resource "aws_instance" "vm" {
  ami           = "ami-12345678"
  instance_type = "t2.micro"
  private_ip    = var.vm_ip
  tags = {
    Name = var.vm_name
  }
}

output "vm_name_output" {
  value = aws_instance.vm.tags["Name"]
}

module "vm1" {
  source  = "./vm_module"
  vm_name = "web-server-1"
  vm_ip   = "10.0.1.10"
}

module "vm2" {
  source  = "./vm_module"
  vm_name = "web-server-2"
  vm_ip   = "10.0.1.11"
}

# Add outputs vm1_name and vm2_name in root main.tf
# Your code here

Need a hint?

Use output "name" { value = module.module_name.output_name } to expose module outputs.