Terraform Basics — Terraform & Infrastructure as Code | Sabaoon Academy

This lesson covers the foundational Terraform workflow that you'll use every day: writing configuration, previewing changes, and applying them.

Installing Terraform

macOS

brew tap hashicorp/tap
brew install hashicorp/tap/terraform

Linux (Ubuntu/Debian)

wget -O- https://apt.releases.hashicorp.com/gpg | sudo gpg --dearmor -o /usr/share/keyrings/hashicorp-archive-keyring.gpg
echo "deb [signed-by=/usr/share/keyrings/hashicorp-archive-keyring.gpg] https://apt.releases.hashicorp.com $(lsb_release -cs) main" | sudo tee /etc/apt/sources.list.d/hashicorp.list
sudo apt update && sudo apt install terraform

Windows

choco install terraform

Verify the installation:

terraform version
# Terraform v1.10.x

HCL Syntax

Terraform uses HashiCorp Configuration Language (HCL). It's designed to be human-readable while remaining machine-parsable.

Blocks

Everything in Terraform is a block:

block_type "label_1" "label_2" {
  argument = "value"

  nested_block {
    argument = "value"
  }
}

Common Block Types

# Provider — which cloud to talk to
provider "aws" {
  region = "us-east-1"
}

# Resource — something to create
resource "aws_s3_bucket" "my_bucket" {
  bucket = "my-app-assets-2026"
}

# Variable — input parameter
variable "environment" {
  type    = string
  default = "dev"
}

# Output — expose a value
output "bucket_url" {
  value = aws_s3_bucket.my_bucket.bucket_domain_name
}

# Data — read existing infrastructure
data "aws_ami" "ubuntu" {
  most_recent = true
  filter {
    name   = "name"
    values = ["ubuntu/images/hvm-ssd/ubuntu-*-amd64-server-*"]
  }
}

# Locals — computed values
locals {
  name_prefix = "${var.environment}-myapp"
}

Types and Expressions

# Strings
name = "web-server"
name = "${var.prefix}-server"  # interpolation

# Numbers
count = 3

# Booleans
enabled = true

# Lists
subnets = ["subnet-abc", "subnet-def"]

# Maps
tags = {
  Name        = "web-server"
  Environment = "production"
}

# Conditionals
instance_type = var.environment == "prod" ? "t3.large" : "t3.micro"

Project Structure

A typical Terraform project:

my-infra/
├── main.tf          # Primary resources
├── variables.tf     # Input variables
├── outputs.tf       # Output values
├── providers.tf     # Provider configuration
├── terraform.tfvars # Variable values (don't commit secrets)
└── .gitignore       # Ignore .terraform/ and *.tfstate

Your .gitignore should include:

.terraform/
*.tfstate
*.tfstate.backup
*.tfvars       # if it contains secrets
.terraform.lock.hcl

The Core Workflow

1. terraform init

Initializes the working directory. Downloads providers and modules.

terraform init

Initializing provider plugins...
- Finding hashicorp/aws versions matching "~> 5.0"...
- Installing hashicorp/aws v5.82.0...

Terraform has been successfully initialized!

Run init when you:

Start a new project
Add or change providers
Add or change modules

2. terraform plan

Shows what Terraform will do without making changes.

terraform plan

Terraform will perform the following actions:

  # aws_s3_bucket.my_bucket will be created
  + resource "aws_s3_bucket" "my_bucket" {
      + bucket = "my-app-assets-2026"
      + id     = (known after apply)
      + arn    = (known after apply)
    }

Plan: 1 to add, 0 to change, 0 to destroy.

The symbols mean:

Symbol	Meaning
`+`	Create
`~`	Update in place
`-`	Destroy
`-/+`	Destroy and recreate

3. terraform apply

Executes the plan. Terraform asks for confirmation before proceeding.

terraform apply

To skip the confirmation prompt (useful in CI/CD):

terraform apply -auto-approve

4. terraform destroy

Removes all resources managed by this configuration.

terraform destroy

This is destructive. Always review the plan before confirming.

Your First Configuration

Create a file called main.tf:

terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 5.0"
    }
  }
  required_version = ">= 1.9.0"
}

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

resource "aws_s3_bucket" "website" {
  bucket = "my-static-site-2026"

  tags = {
    Name        = "Static Website"
    Environment = "dev"
  }
}

output "bucket_name" {
  value = aws_s3_bucket.website.bucket
}

Run it:

terraform init    # Download the AWS provider
terraform plan    # Preview the S3 bucket creation
terraform apply   # Create the bucket
terraform output  # See the bucket name

Useful Commands

Command	Purpose
`terraform fmt`	Format your `.tf` files
`terraform validate`	Check syntax without connecting to providers
`terraform show`	Show current state
`terraform output`	Display output values
`terraform state list`	List all resources in state
`terraform refresh`	Update state to match real infrastructure

Summary

Install Terraform and verify with terraform version
HCL uses blocks, arguments, and expressions to describe infrastructure
The core workflow is init → plan → apply → destroy
Always review the plan before applying changes
Use terraform fmt and terraform validate to keep your code clean