Understanding Infrastructure as Code with Terraform

What Is Terraform?

Terraform is an infrastructure-as-code tool that lets you define cloud resources in declarative configuration files. It supports multiple providers (AWS, GCP, Azure, Proxmox, and more).

Installation

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 -y terraform

Basic Configuration

Create main.tf:

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

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

resource "aws_instance" "web" {
  ami           = "ami-0c55b159cbfafe1f0"
  instance_type = "t3.micro"

  tags = {
    Name = "web-server"
  }
}

Core Workflow

# Initialize (download providers)
terraform init

# Preview changes
terraform plan

# Apply changes
terraform apply

# Destroy resources
terraform destroy

State Management

Terraform tracks resource state in terraform.tfstate. For team use, store state remotely:

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

Variables and Outputs

variable "instance_type" {
  description = "EC2 instance type"
  default     = "t3.micro"
}

output "public_ip" {
  value = aws_instance.web.public_ip
}

Key Concepts

• Declarative — you describe what you want, Terraform figures out how
• Plan before apply — always review changes before applying
• State file — never edit manually, use terraform state commands
• Modules — reusable components for common patterns