terraform iac devops cloud infrastructure

Terraform basics: providers, resources, and state

Ryan Nakamura Feb 2026

3 tabs

# Configure Terraform
terraform {
  required_version = ">= 1.6.0"

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

  # Remote state backend
  backend "s3" {
    bucket         = "mycompany-terraform-state"
    key            = "production/terraform.tfstate"
    region         = "us-east-1"
    dynamodb_table = "terraform-locks"
    encrypt        = true
  }
}

# Configure provider
provider "aws" {
  region = var.aws_region

  default_tags {
    tags = {
      Environment = var.environment
      ManagedBy   = "terraform"
      Project     = var.project_name
    }
  }
}

# VPC
resource "aws_vpc" "main" {
  cidr_block           = var.vpc_cidr
  enable_dns_hostnames = true
  enable_dns_support   = true

  tags = {
    Name = "${var.project_name}-vpc"
  }
}

# Public subnets
resource "aws_subnet" "public" {
  count = length(var.availability_zones)

  vpc_id                  = aws_vpc.main.id
  cidr_block              = cidrsubnet(var.vpc_cidr, 8, count.index)
  availability_zone       = var.availability_zones[count.index]
  map_public_ip_on_launch = true

  tags = {
    Name = "${var.project_name}-public-${var.availability_zones[count.index]}"
    Type = "public"
  }
}

# Private subnets
resource "aws_subnet" "private" {
  count = length(var.availability_zones)

  vpc_id            = aws_vpc.main.id
  cidr_block        = cidrsubnet(var.vpc_cidr, 8, count.index + 10)
  availability_zone = var.availability_zones[count.index]

  tags = {
    Name = "${var.project_name}-private-${var.availability_zones[count.index]}"
    Type = "private"
  }
}

# Internet Gateway
resource "aws_internet_gateway" "main" {
  vpc_id = aws_vpc.main.id

  tags = {
    Name = "${var.project_name}-igw"
  }
}

# NAT Gateway
resource "aws_eip" "nat" {
  domain = "vpc"
}

resource "aws_nat_gateway" "main" {
  allocation_id = aws_eip.nat.id
  subnet_id     = aws_subnet.public[0].id

  tags = {
    Name = "${var.project_name}-nat"
  }
}

# Route tables
resource "aws_route_table" "public" {
  vpc_id = aws_vpc.main.id

  route {
    cidr_block = "0.0.0.0/0"
    gateway_id = aws_internet_gateway.main.id
  }

  tags = {
    Name = "${var.project_name}-public-rt"
  }
}

resource "aws_route_table" "private" {
  vpc_id = aws_vpc.main.id

  route {
    cidr_block     = "0.0.0.0/0"
    nat_gateway_id = aws_nat_gateway.main.id
  }

  tags = {
    Name = "${var.project_name}-private-rt"
  }
}

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

variable "environment" {
  description = "Environment name"
  type        = string
  validation {
    condition     = contains(["dev", "staging", "production"], var.environment)
    error_message = "Environment must be dev, staging, or production."
  }
}

variable "project_name" {
  description = "Project name for resource naming"
  type        = string
}

variable "vpc_cidr" {
  description = "VPC CIDR block"
  type        = string
  default     = "10.0.0.0/16"
}

variable "availability_zones" {
  description = "List of availability zones"
  type        = list(string)
  default     = ["us-east-1a", "us-east-1b", "us-east-1c"]
}

#!/bin/bash
# Terraform workflow commands

# Initialize (download providers, configure backend)
terraform init

# Validate configuration
terraform validate

# Format code
terraform fmt -recursive

# Plan changes
terraform plan -out=tfplan
terraform plan -var-file=production.tfvars -out=tfplan

# Apply changes
terraform apply tfplan
terraform apply -auto-approve     # Skip confirmation (CI/CD)

# Show current state
terraform show
terraform state list
terraform state show aws_vpc.main

# Import existing resources
terraform import aws_vpc.main vpc-12345

# Destroy infrastructure
terraform destroy
terraform destroy -target=aws_instance.web

# Workspace management
terraform workspace list
terraform workspace new staging
terraform workspace select production

# Output values
terraform output
terraform output -json vpc_id

3 files · hcl, bash Explain with highlit

Terraform is an infrastructure as code (IaC) tool that provisions cloud resources declaratively. Configuration files use HCL (HashiCorp Configuration Language). The provider block configures cloud providers like AWS, GCP, or Azure. resource blocks define infrastructure components. terraform init downloads providers. terraform plan previews changes. terraform apply provisions infrastructure. State files track managed resources—store them remotely in S3 or Terraform Cloud for team collaboration. The terraform.tfvars file sets variable values. data sources read existing infrastructure. output values expose resource attributes. Backend configuration determines where state is stored. The plan-apply workflow ensures predictable infrastructure changes.