Terraform Getting Started

Overview

Terraform is an infrastructure-as-code tool that lets you define cloud resources in declarative configuration files and manage their full lifecycle with a consistent CLI workflow. This guide walks through your first Terraform deployment — the equivalent of "Hello, World" for infrastructure.

The fundamental workflow

Every Terraform project follows four core commands:

terraform init       # Initialize the working directory; download providers.
terraform plan       # Preview changes before applying.
terraform apply      # Create/update resources based on configuration.
terraform destroy    # Tear down all managed resources.

This loop — write config → init → plan → apply → destroy — is the foundation of every Terraform project, from a single EC2 instance to multi-account architectures.

Your first configuration

main.tf

terraform {
  required_version = ">= 1.0.0, < 2.0.0"

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

provider "aws" {
  region = "us-east-2"
}

resource "aws_instance" "hello" {
  ami           = "ami-0fb653ca2d3203ac1"
  instance_type = "t2.micro"

  tags = {
    Name = "terraform-hello"
  }
}

Key blocks explained

Block	Purpose
terraform { }	Configure Terraform itself — version constraints and provider requirements.
required_providers { }	Declare which providers are needed and where to get them (source).
provider "aws" { }	Configure the AWS provider — region, credentials, and other settings.
resource "aws_instance" "hello" { }	Define an infrastructure resource. This creates one EC2 instance.

Running it

# 1. Initialize the project
terraform init

# Output:
# Initializing the backend...
# Initializing provider plugins...
# - Finding hashicorp/aws versions matching "~> 5.0"...
# - Installing hashicorp/aws v5...
# Terraform has been successfully initialized!

# 2. Preview changes
terraform plan

# Output: + aws_instance.hello will be created
# Plan: 1 to add, 0 to change, 0 to destroy.

# 3. Apply the changes
terraform apply

# Terraform shows the plan again and asks for confirmation.
# Type 'yes' to proceed.

# 4. Tear it down
terraform destroy

# Removes the EC2 instance. Type 'yes' to confirm.

What happens under the hood

When you run terraform apply, Terraform:

1. Reads your configuration files (*.tf) and builds a dependency graph.
2. Compares the desired state (your config) with the actual state (recorded in terraform.tfstate).
3. Generates an execution plan: which resources to create, update, or destroy.
4. Calls the AWS API (via the provider) to create the EC2 instance.
5. Writes the new state to terraform.tfstate.

The state file

After applying, you'll find terraform.tfstate — a JSON file that maps your configuration to real AWS resources. Treat it as sensitive: it contains resource IDs, attributes, and may include secrets.

For team environments, never store state in version control. Instead, use a remote backend like S3 with DynamoDB locking (see Managing Terraform State).

Common pitfalls

• Forgot terraform init? Run it when you add new providers or clone a project for the first time.
• State drift: If someone changes a resource outside Terraform (e.g., in the AWS console), terraform plan detects the drift and offers to reconcile it.
• Credentials: Terraform reads AWS credentials from the standard locations (environment variables, ~/.aws/credentials, IAM roles). Set AWS_PROFILE or AWS_ACCESS_KEY_ID/AWS_SECRET_ACCESS_KEY.

See also

• Terraform Configuration Syntax — variables, outputs, and data sources
• Managing Terraform State — remote state backends and locking