# 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.

---

## Basics First

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

```plaintext
Init → Write → Plan → Apply
```

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

---

## First Code Snippets

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

```plaintext
// 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**:

```plaintext
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](https://www.youtube.com/watch?v=QhmFnlbbwP4). I personally prefer using **WSL on Windows** for development.

---

## Solution Code

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

```plaintext
// 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]
}
```

---

### References

* [AWS VPC & Subnets](https://www.youtube.com/watch?v=bGDMeD6kOz0)
    
* [AWS Subnets Docs](https://registry.terraform.io/providers/-/aws/latest/docs/resources/subnet)
    
* [Understanding CIDR and Subnets](https://www.youtube.com/results?search_query=understanding+CIDR+subnets+aws)
    

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**Tags:** `aws`, `basics`, `getstarted`, `iac`, `terraform`**Category:** `Infra as Code`