Week 7 - Day 2: Terraform Basics

⏱ Duration: 5 Hours

📚 Learning Objectives

Understand Terraform providers and resources
Work with variables and outputs
Master terraform init, plan, apply workflow
Learn Terraform file structure and syntax

📖 Core Concepts (2 Hours)

Terraform File Structure

my-terraform-project/
├── main.tf          # Main configuration (resources)
├── variables.tf     # Input variable declarations
├── outputs.tf       # Output value declarations
├── terraform.tfvars # Variable values (don't commit secrets!)
├── providers.tf     # Provider configurations
└── .terraform/      # Downloaded providers (gitignore this)

Providers

Providers are plugins that Terraform uses to interact with cloud APIs.

# providers.tf
terraform {
  required_version = ">= 1.0.0"
  
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 5.0"
    }
  }
}

# Configure the AWS Provider
provider "aws" {
  region = "us-east-1"
  
  # Optional: Use specific profile
  # profile = "my-aws-profile"
  
  default_tags {
    tags = {
      Environment = "Development"
      ManagedBy   = "Terraform"
    }
  }
}

Resources

Resources are the infrastructure objects Terraform manages.

# Resource syntax:
# resource "TYPE" "NAME" {
#   argument = value
# }

# Example: S3 Bucket
resource "aws_s3_bucket" "my_bucket" {
  bucket = "my-unique-bucket-name-12345"
  
  tags = {
    Name = "My Terraform Bucket"
  }
}

# Reference other resources
resource "aws_s3_bucket_versioning" "my_bucket_versioning" {
  bucket = aws_s3_bucket.my_bucket.id  # Reference!
  
  versioning_configuration {
    status = "Enabled"
  }
}

Variables

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

variable "instance_type" {
  description = "EC2 instance type"
  type        = string
  default     = "t2.micro"
}

variable "allowed_ports" {
  description = "List of allowed ports"
  type        = list(number)
  default     = [22, 80, 443]
}

variable "tags" {
  description = "Tags for resources"
  type        = map(string)
  default = {
    Environment = "dev"
    Project     = "demo"
  }
}

# Use variables with var.name
provider "aws" {
  region = var.region
}

Variable Values

# terraform.tfvars - Set values
region        = "us-west-2"
instance_type = "t3.micro"
allowed_ports = [22, 80, 443, 8080]
tags = {
  Environment = "production"
  Project     = "webapp"
}

# Or pass via command line:
terraform apply -var="region=us-west-2"

# Or environment variables:
export TF_VAR_region="us-west-2"

Outputs

# outputs.tf
output "bucket_name" {
  description = "Name of the S3 bucket"
  value       = aws_s3_bucket.my_bucket.id
}

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

output "bucket_domain" {
  description = "Domain name of the bucket"
  value       = aws_s3_bucket.my_bucket.bucket_domain_name
}

# After apply, view outputs:
# terraform output
# terraform output bucket_name

Terraform Workflow

┌─────────────────────────────────────────────┐
│              terraform init                  │
│  • Downloads provider plugins                │
│  • Initializes backend                       │
│  • Creates .terraform directory              │
└─────────────────┬───────────────────────────┘
                  ▼
┌─────────────────────────────────────────────┐
│              terraform plan                  │
│  • Reads current state                       │
│  • Compares with configuration               │
│  • Shows what will change                    │
│  • Does NOT make any changes                 │
└─────────────────┬───────────────────────────┘
                  ▼
┌─────────────────────────────────────────────┐
│              terraform apply                 │
│  • Executes the plan                         │
│  • Creates/updates/deletes resources         │
│  • Updates state file                        │
└─────────────────┬───────────────────────────┘
                  ▼
┌─────────────────────────────────────────────┐
│             terraform destroy                │
│  • Removes all managed resources             │
│  • Use when done to avoid charges            │
└─────────────────────────────────────────────┘

🔬 Hands-on Lab (2.5 Hours)

Lab 1: Create S3 Bucket with Variables

# Create project structure
mkdir -p ~/terraform-labs/lab2-s3
cd ~/terraform-labs/lab2-s3

# providers.tf
cat > providers.tf << 'EOF'
terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 5.0"
    }
  }
}

provider "aws" {
  region = var.region
}
EOF

# variables.tf
cat > variables.tf << 'EOF'
variable "region" {
  description = "AWS region"
  type        = string
  default     = "us-east-1"
}

variable "bucket_prefix" {
  description = "Prefix for bucket name"
  type        = string
  default     = "my-terraform"
}

variable "environment" {
  description = "Environment name"
  type        = string
  default     = "dev"
}
EOF

# main.tf
cat > main.tf << 'EOF'
resource "aws_s3_bucket" "demo" {
  bucket = "${var.bucket_prefix}-${var.environment}-${random_id.suffix.hex}"
  
  tags = {
    Name        = "Demo Bucket"
    Environment = var.environment
    ManagedBy   = "Terraform"
  }
}

resource "random_id" "suffix" {
  byte_length = 4
}

resource "aws_s3_bucket_versioning" "demo" {
  bucket = aws_s3_bucket.demo.id
  versioning_configuration {
    status = "Enabled"
  }
}
EOF

# outputs.tf
cat > outputs.tf << 'EOF'
output "bucket_name" {
  value = aws_s3_bucket.demo.id
}

output "bucket_arn" {
  value = aws_s3_bucket.demo.arn
}

output "bucket_region" {
  value = aws_s3_bucket.demo.region
}
EOF

Lab 2: Run Terraform Commands

# Initialize - download providers
terraform init

# Validate configuration
terraform validate

# Format code (auto-fix formatting)
terraform fmt

# Plan - see what will be created
terraform plan

# Apply - create resources
terraform apply
# Type 'yes' when prompted

# View outputs
terraform output
terraform output bucket_name

# View state
terraform state list
terraform state show aws_s3_bucket.demo

# Destroy when done (save money!)
terraform destroy

Lab 3: Using tfvars Files

# Create different environments
cat > dev.tfvars << 'EOF'
region      = "us-east-1"
environment = "dev"
bucket_prefix = "myapp"
EOF

cat > prod.tfvars << 'EOF'
region      = "us-west-2"
environment = "prod"
bucket_prefix = "myapp"
EOF

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

# Or for production
terraform plan -var-file="prod.tfvars"

✅ Day 2 Checklist

Understand providers and how to configure them
Can create and reference resources
Know how to use variables and outputs
Master init, plan, apply, destroy workflow
Created S3 bucket with Terraform

← Day 1: IaC Intro Day 3: Terraform AWS →