Infrastructure as Code with Terraform

What is Terraform?

Terraform lets you define infrastructure in code (HCL — HashiCorp Configuration Language). Instead of clicking through cloud dashboards, you write declarative configs and terraform apply.

Installation

wget -O- https://apt.releases.hashicorp.com/gpg | sudo gpg --dearmor -o /usr/share/keyrings/hashicorp.gpg
echo "deb [signed-by=/usr/share/keyrings/hashicorp.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 -y terraform

Basic Structure

project/
├── main.tf           # Primary resources
├── variables.tf      # Input variables
├── outputs.tf        # Output values
├── terraform.tfvars  # Variable values (gitignored)
└── providers.tf      # Provider configuration

Example: VPS with DNS

# providers.tf
terraform {
  required_providers {
    digitalocean = {
      source  = "digitalocean/digitalocean"
      version = "~> 2.0"
    }
    cloudflare = {
      source  = "cloudflare/cloudflare"
      version = "~> 4.0"
    }
  }
}

# variables.tf
variable "domain" {
  type    = string
  default = "example.com"
}

variable "region" {
  type    = string
  default = "nyc1"
}

# main.tf
resource "digitalocean_droplet" "web" {
  name     = "web-server"
  region   = var.region
  size     = "s-2vcpu-4gb"
  image    = "ubuntu-24-04-x64"
  ssh_keys = [digitalocean_ssh_key.deploy.fingerprint]
}

resource "cloudflare_record" "web" {
  zone_id = var.cloudflare_zone_id
  name    = var.domain
  value   = digitalocean_droplet.web.ipv4_address
  type    = "A"
  proxied = true
}

# outputs.tf
output "server_ip" {
  value = digitalocean_droplet.web.ipv4_address
}

Workflow

# Initialize (download providers)
terraform init

# Preview changes
terraform plan

# Apply changes
terraform apply

# Destroy everything
terraform destroy

State Management

Terraform tracks resources in a state file. For teams, store state remotely:

terraform {
  backend "s3" {
    bucket = "my-terraform-state"
    key    = "prod/terraform.tfstate"
    region = "us-east-1"
  }
}

Best Practices

Warning Never store terraform.tfstate in git — it may contain secrets. Use remote backends (S3, Terraform Cloud, etc.) for team collaboration.