8. 🏗️ Terraform: Infrastructure as Code (IaC) from Scratch for DevOps Engineers

🎯 Why Terraform?

Manual infrastructure creation leads to:

• Configuration drift

• Human errors

• No version control

Terraform solves this using Infrastructure as Code (IaC).

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🔹 What is Terraform?

Terraform is an open-source IaC tool by HashiCorp that:

• Automates infrastructure provisioning

• Works across clouds (AWS, Azure, GCP)

• Uses declarative configuration

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🔹 Terraform vs Manual Provisioning

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🔹 Terraform Workflow

terraform init
terraform plan
terraform apply
terraform destroy

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🔹 Terraform Configuration Files

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🔹 Terraform Provider Example

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

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🔹 Create an EC2 Instance (Basic)

resource "aws_instance" "web" {
  ami           = "ami-0abcd1234"
  instance_type = "t2.micro"

  tags = {
    Name = "Terraform-EC2"
  }
}

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🔹 Terraform Variables

variable "instance_type" {
  default = "t2.micro"
}

Usage:

instance_type = var.instance_type

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🔹 Terraform Output

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

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🔹 What is Terraform State?

State file (terraform.tfstate):

• Maps real infra to code

• Tracks resource changes

⚠️ Never edit manually.

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🔹 Why Remote Backend (S3 + DynamoDB)?

• Centralized state

• Team collaboration

• State locking

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Backend Example

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

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🔹 What is State Locking?

Prevents:

• Multiple users applying changes simultaneously

• State corruption

DynamoDB handles locking.

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🔹 Terraform Plan vs Apply

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🔹 Terraform Modules

Modules allow:

• Reusability

• Clean structure

• Standardization

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Simple Module Structure

modules/
 └── ec2/
     ├── main.tf
     ├── variables.tf
     └── outputs.tf

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🔹 Terraform Best Practices

• Use remote backend

• Lock state

• Use modules

• Separate environments

• Never commit state file

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🔹 Terraform Destroy (Use Carefully)

terraform destroy

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🔹 Real Production Scenario

Issue: Infra drift across environments
Fix: Terraform applied consistently
Result: Zero manual changes, stable infra

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🎯 Interview Takeaways

• Terraform is declarative

• State is critical

• Remote backend is mandatory

• plan before apply

• Modules are reusable