Basics of IaC with Terraform

Introduction

In this series, we are going to focus our attention on Terraform. This series is different in the sense that I will be learning along as I write about it.

Terraform is an open-source Infrastructure as Code (IaC) tool designed by HashiCorp. It enables users to define and provision infrastructure and resources in a declarative manner using a high-level configuration language.

One key thing about Terraform that makes it so powerful is that it is a cloud-agnostic tool, allowing provisioning of infrastructure across 100+ providers including AWS, Azure, and GCP.

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Basics First

Before diving into the code, let’s walk through some basics first. Every Terraform project follows a standard lifecycle:

Init → Write → Plan → Apply

This lifecycle is consistent across all Terraform projects and defines how infrastructure is initialized, configured, reviewed, and deployed.

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First Code Snippets

Any Terraform project starts by defining the provider. Here’s a simple example:

// This defines and sets the provider for the Terraform project.
// Terraform will use this to download the required provider code
// and interact with the provider APIs.

provider "google" {
  credentials = file("creds.json")
  project     = "Hello-World"
  region      = "us-east-1"
}

Once the provider is set, you can start creating resources:

resource "aws_instance" "hello-instance" {
  ami           = "ami-id-here"
  instance_type = "t2-micro"
}

In the above snippet:

• aws_instance defines the type of resource.

• "hello-instance" is the user-defined name.

• You can later refer to it as aws_instance.hello-instance.

There’s also a data block, which is useful for referencing shared configuration such as AMI IDs or instance types without repeating values across multiple resources. We’ll use it later when the need arises.

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Example 1 — Create an EC2 Instance

In this example, we’ll create an EC2 instance using Terraform. To set up Terraform and AWS CLI, follow this video tutorial. I personally prefer using WSL on Windows for development.

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Solution Code

If required, you may need to read up about subnets and networking first.

// Setup the provider and mention the profile Terraform should use for login
provider "aws" {
  region  = "us-east-1"
  profile = "terraform"
}

// Step 1: Create a VPC for development
resource "aws_vpc" "vpcdev" {
  cidr_block = "10.0.0.0/16"

  tags = {
    environment = "development"
  }
}

// Step 2: Create a subnet in the VPC created above
resource "aws_subnet" "devsubnet1" {
  vpc_id            = aws_vpc.vpcdev.id
  cidr_block        = "10.0.1.0/24"
  availability_zone = "us-east-1a"

  depends_on = [aws_vpc.vpcdev]
}

// Step 3: Create an EC2 instance in the subnet
resource "aws_instance" "devvm1" {
  ami           = "ami-0be2609ba883822ec"
  instance_type = "t2.micro"
  subnet_id     = aws_subnet.devsubnet1.id

  depends_on = [aws_subnet.devsubnet1]
}

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References

• AWS VPC & Subnets

• AWS Subnets Docs

• Understanding CIDR and Subnets

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Tags: aws, basics, getstarted, iac, terraformCategory: Infra as Code