Terraform Fundamentals (IaC)

Terraform is infrastructure-as-code.

Instead of manually creating resources (VMs, networks, IAM roles), you describe desired infrastructure in .tf files. Terraform then computes what to change.

Theory first: declarative infrastructure lifecycle

Terraform is a declarative model where configuration defines target state and state files track current reality. Planning is the critical feedback phase between intent and mutation.

Treat the workflow as a lifecycle: design the desired architecture, review planned drift and impact, then apply controlled changes. This reduces accidental infrastructure mutations and improves team safety.

Learning outcomes

By the end you’ll know:

• the Terraform workflow (init/validate/plan/apply)
• what providers, resources, variables, outputs are
• how state influences changes

1) Terraform workflow

Typical commands:

terraform init
terraform validate
terraform plan
terraform apply

2) A minimal example

main.tf

terraform {
  required_version = ">= 1.6.0"
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 5.0"
    }
  }
}

provider "aws" {
  region = var.aws_region
}

resource "aws_s3_bucket" "example" {
  bucket = "my-unique-bucket-name-12345"
}

variables.tf

variable "aws_region" {
  type    = string
  default = "us-east-1"
}

outputs.tf

output "bucket_name" {
  value = aws_s3_bucket.example.bucket
}

3) State (important)

State is stored in terraform.tfstate locally by default. In real teams you typically use remote state (e.g. S3 + DynamoDB locking) so:

• multiple engineers can work safely
• Terraform uses locking to prevent concurrent updates

4) Plan before apply

Always review terraform plan:

• what will be created
• what will be changed
• what might be destroyed

5) Modules: reuse configuration

A module is a folder containing Terraform code that can be called like a component.

Example:

module "vpc" {
  source = "./modules/vpc"

  cidr_block = "10.0.0.0/16"
}

6) Next steps

Next tutorials:

• Terraform modules (reusable patterns)
• Terraform plan/apply in CI/CD (GitHub Actions)
• Terraform best practices for state and secrets