What is Terraform Basics?

Learn HashiCorp Terraform fundamentals — providers, resources, variables, outputs, state management, and your first infrastructure deployment

Terraform Basics - Cloud & Kubernetes Tutorial | TechLead

What is Terraform?

Terraform is an open-source Infrastructure as Code (IaC) tool created by HashiCorp. It lets you define and provision infrastructure using a declarative configuration language called HCL (HashiCorp Configuration Language). Terraform supports hundreds of cloud providers and services, enabling you to manage your entire infrastructure lifecycle — create, update, and destroy — through code.

Why Terraform?

Multi-Cloud: Works with AWS, GCP, Azure, Kubernetes, and 3000+ providers
Declarative: Define what you want, not how to get there
State Management: Tracks the real-world state of your infrastructure
Plan Before Apply: Preview changes before making them
Modular: Reuse infrastructure code with modules
Version Controlled: Infrastructure changes are tracked in Git like application code

Installing Terraform

# macOS
brew tap hashicorp/tap
brew install hashicorp/tap/terraform

# Linux
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

# Verify installation
terraform version

# Enable autocompletion
terraform -install-autocomplete

Terraform Core Workflow

Terraform follows a simple workflow: Write configuration, Plan changes, and Apply the plan. This three-step process ensures you always know what will change before it happens.

# Initialize the working directory (download providers)
terraform init

# Format configuration files
terraform fmt

# Validate configuration syntax
terraform validate

# Preview changes (dry run)
terraform plan

# Apply changes
terraform apply

# Apply with auto-approve (CI/CD pipelines)
terraform apply -auto-approve

# Destroy all resources
terraform destroy

# Show current state
terraform show

# List resources in state
terraform state list

Your First Terraform Configuration

# main.tf - AWS S3 bucket + CloudFront distribution

terraform {
  required_version = ">= 1.5"

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

  # Remote state storage (recommended for teams)
  backend "s3" {
    bucket         = "my-terraform-state-bucket"
    key            = "production/terraform.tfstate"
    region         = "us-east-1"
    dynamodb_table = "terraform-locks"
    encrypt        = true
  }
}

provider "aws" {
  region = var.aws_region

  default_tags {
    tags = {
      Environment = var.environment
      ManagedBy   = "terraform"
      Project     = var.project_name
    }
  }
}

# S3 bucket for static website
resource "aws_s3_bucket" "website" {
  bucket = "${var.project_name}-${var.environment}-website"
}

resource "aws_s3_bucket_website_configuration" "website" {
  bucket = aws_s3_bucket.website.id

  index_document {
    suffix = "index.html"
  }

  error_document {
    key = "404.html"
  }
}

resource "aws_s3_bucket_public_access_block" "website" {
  bucket = aws_s3_bucket.website.id

  block_public_acls       = false
  block_public_policy     = false
  ignore_public_acls      = false
  restrict_public_buckets = false
}

resource "aws_s3_bucket_policy" "website" {
  bucket = aws_s3_bucket.website.id

  policy = jsonencode({
    Version = "2012-10-17"
    Statement = [{
      Sid       = "PublicReadGetObject"
      Effect    = "Allow"
      Principal = "*"
      Action    = "s3:GetObject"
      Resource  = "${aws_s3_bucket.website.arn}/*"
    }]
  })
}

Variables and Outputs

# variables.tf
variable "aws_region" {
  description = "AWS region to deploy resources"
  type        = string
  default     = "us-east-1"
}

variable "environment" {
  description = "Environment name (development, staging, production)"
  type        = string

  validation {
    condition     = contains(["development", "staging", "production"], var.environment)
    error_message = "Environment must be development, staging, or production."
  }
}

variable "project_name" {
  description = "Project name used for resource naming"
  type        = string
}

variable "instance_count" {
  description = "Number of EC2 instances"
  type        = number
  default     = 2
}

variable "allowed_cidrs" {
  description = "List of CIDR blocks allowed to access the application"
  type        = list(string)
  default     = ["0.0.0.0/0"]
}

variable "tags" {
  description = "Additional tags for resources"
  type        = map(string)
  default     = {}
}

# outputs.tf
output "website_url" {
  description = "URL of the S3 static website"
  value       = aws_s3_bucket_website_configuration.website.website_endpoint
}

output "bucket_arn" {
  description = "ARN of the S3 bucket"
  value       = aws_s3_bucket.website.arn
}

output "bucket_name" {
  description = "Name of the S3 bucket"
  value       = aws_s3_bucket.website.id
}

# terraform.tfvars (environment-specific values)
aws_region   = "us-east-1"
environment  = "production"
project_name = "my-web-app"

# Apply with var file
terraform plan -var-file="production.tfvars"
terraform apply -var-file="production.tfvars"

Key Takeaways

Terraform is the leading multi-cloud IaC tool — write once, deploy anywhere
The workflow is: init, plan, apply — always review the plan before applying
Use variables for reusable configs, outputs to expose values to other modules
Store state remotely (S3, GCS, Azure Blob) with locking for team collaboration
Version control all Terraform code and use code review for infrastructure changes

Terraform Basics

What is Terraform?

Why Terraform?

Installing Terraform

Terraform Core Workflow

Your First Terraform Configuration

Variables and Outputs

Key Takeaways

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