Overview

Terraform is an Infrastructure as Code (IaC) tool by HashiCorp that allows you to define, provision, and manage infrastructure across cloud providers using declarative configuration files.

Why Terraform¶

• Ideal for creating and managing infrastructure.
• Uses HCL (HashiCorp Configuration Language) — a human-readable, declarative language.

Example¶

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

How Terraform Communicates with Cloud Providers¶

1. Providers (Plugins) Terraform uses provider plugins to communicate with clouds.

2. hashicorp/aws for AWS

3. hashicorp/azurerm for Azure

4. hashicorp/google for GCP

5. APIs Each provider calls the official cloud API (REST or SDK) to create resources.

6. Authentication Terraform needs credentials to access APIs:

provider "aws" {
  access_key = "YOUR_ACCESS_KEY"
  secret_key = "YOUR_SECRET_KEY"
  region     = "us-east-1"
}

1. Terraform Workflow

2. init → Download providers

3. plan → Preview changes
4. apply → Create or modify resources
5. state → Save results locally or remotely

Example Flow¶

resource "aws_s3_bucket" "demo" {
  bucket = "my-demo-bucket"
}

Terraform uses the AWS provider to authenticate, send an API call, and record the result in terraform.tfstate.

Summary: Terraform communicates through provider plugins that use official cloud APIs to create and manage resources.

AWS CLI Installation & Configuration¶

1. Install AWS CLI¶

macOS

brew install awscli
aws --version

Windows

choco install awscli
aws --version

Manual installers are available at: https://docs.aws.amazon.com/cli/latest/userguide/getting-started-install.html

2. Configure AWS CLI¶

aws configure

Enter:

AWS Access Key ID [None]: test
AWS Secret Access Key [None]: test
Default region name [None]: us-east-1
Default output format [None]: json

Configuration files:

~/.aws/credentials
~/.aws/config

Windows path:

C:\Users\<username>\.aws\

3. Test Configuration¶

aws s3 ls

With LocalStack:

aws --endpoint-url=http://localhost:4566 s3 ls

4. Optional: Custom Profiles¶

aws configure --profile localstack
aws --profile localstack --endpoint-url=http://localhost:4566 s3 ls

LocalStack Setup¶

LocalStack emulates AWS services locally using Docker — perfect for testing Terraform and AWS CLI without real AWS credentials.

Why Use LocalStack¶

• Avoid AWS costs
• Work offline
• Fast and safe testing
• Supports S3, EC2, Lambda, DynamoDB, and more

1. Prerequisites¶

2. Install LocalStack¶

pip install localstack awscli-local
localstack --version

3. Start LocalStack¶

localstack start

Runs on http://localhost:4566.

4. Web Dashboard¶

Terminal

5. Test¶

awslocal s3 ls
awslocal s3 mb s3://demo-bucket

6. Docker Compose Example¶

version: "3.8"
services:
  localstack:
    image: localstack/localstack
    ports:
      - "4566:4566"
    environment:
      - SERVICES=s3,ec2,lambda
      - DEBUG=1
    volumes:
      - "./localstack:/var/lib/localstack"

Run:

docker-compose up

Terraform + LocalStack Integration¶

Project Structure¶

terraform-localstack-demo/
├── main.tf
├── provider.tf
├── outputs.tf
└── hello.txt

Step 1: Create a Test File¶

echo "Hello from Terraform + LocalStack!" > hello.txt

Step 2: provider.tf¶

terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 5.0"
    }
  }
  required_version = ">= 1.5.0"
}

provider "aws" {
  region                      = "us-east-1"
  access_key                  = "test"
  secret_key                  = "test"
  s3_force_path_style         = true
  skip_credentials_validation = true
  skip_metadata_api_check     = true
  skip_requesting_account_id  = true
  endpoints {
    s3 = "http://localhost:4566"
  }
}

Step 3: main.tf¶

resource "aws_s3_bucket" "demo" {
  bucket = "terraform-localstack-demo"
}

resource "aws_s3_object" "file_upload" {
  bucket = aws_s3_bucket.demo.id
  key    = "hello.txt"
  source = "hello.txt"
  etag   = filemd5("hello.txt")
}

Step 4: outputs.tf¶

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

Step 5: Deploy¶

terraform init
terraform plan
terraform apply -auto-approve

Verify:

awslocal s3 ls
awslocal s3 ls s3://terraform-localstack-demo/

Cleanup and Destroy¶

Destroy Resources¶

terraform destroy -auto-approve

Output:

Destroy complete! Resources: 2 destroyed.

Optional: Preview Destroy¶

terraform plan -destroy

Verify Deletion¶

awslocal s3 ls

Reset LocalStack (Optional)¶

localstack stop
docker rm -f localstack
docker volume prune -f
localstack start