🧾 Terraform Cheat Sheet: The Ultimate Reference for Infrastructure as Code (2025)

Learn and master Terraform with this complete cheat sheet — from basics to advanced automation.

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🚀 What is Terraform?

Terraform by HashiCorp is a declarative Infrastructure as Code (IaC) tool that allows you to provision, manage, and destroy infrastructure using human-readable configuration files.

In short: you write .tf code to define your cloud infrastructure, and Terraform makes it real — across AWS, Azure, GCP, and more.

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📁 Typical Terraform Project Structure

my-project/
├── main.tf          # Core infrastructure code
├── variables.tf     # Variable declarations
├── outputs.tf       # Outputs (e.g., public IPs)
├── terraform.tfvars # Actual variable values
├── backend.tf       # Remote backend config (S3, Terraform Cloud)

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⚙️ Common Terraform Commands

Command	Description
terraform init	Initializes working directory (downloads provider plugins)
terraform plan	Previews what Terraform will change
terraform apply	Applies changes to reach desired state
terraform destroy	Deletes all resources created
terraform validate	Checks for syntax correctness
terraform fmt	Auto-formats .tf files
terraform output	Displays output values
terraform show	Shows current state
terraform taint <resource>	Marks resource for recreation on next apply
terraform state list	Lists all managed resources

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📘 Terraform Configuration Syntax (HCL)

🔹 1. Providers

provider "aws" {
  region = var.region
}

🔹 2. Resources

resource "aws_instance" "web" {
  ami           = var.ami_id
  instance_type = "t2.micro"
}

🔹 3. Variables

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

Use in code:

region = var.region

🔹 4. Outputs

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

🔹 5. Locals

locals {
  name_tag = "web-${var.environment}"
}

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📦 Remote Backends (S3 Example)

terraform {
  backend "s3" {
    bucket         = "my-tf-state"
    key            = "env/dev/terraform.tfstate"
    region         = "us-east-1"
    dynamodb_table = "tf-locks"
  }
}

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📦 Modules (Reusable Blocks)

module "vpc" {
  source     = "terraform-aws-modules/vpc/aws"
  name       = "my-vpc"
  cidr_block = "10.0.0.0/16"
}

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🔐 Security Best Practices

Task	Tool
Lint & secure configs	TFLint, Checkov, TFSec
Secrets management	Avoid hardcoding – use Vault, SOPS, environment variables
Policy enforcement	OPA, Sentinel (in Terraform Cloud)

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🧪 Testing Terraform

Tool	Description
terraform validate	Syntax checks
TFLint	Linting and best practices
Checkov	Static security scanning
Terratest	Integration testing using Go

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🔄 Useful Patterns & Snippets

🔸 Conditional Logic

resource "aws_instance" "web" {
  count = var.create_instance ? 1 : 0
}

🔸 Dynamic Blocks

resource "aws_security_group" "example" {
  dynamic "ingress" {
    for_each = var.ingress_rules
    content {
      from_port   = ingress.value.from_port
      to_port     = ingress.value.to_port
      protocol    = ingress.value.protocol
      cidr_blocks = ingress.value.cidr_blocks
    }
  }
}

🔸 Workspaces

terraform workspace list
terraform workspace new staging
terraform workspace select staging

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🧠 Best Practices

✅ Use terraform plan before every apply
✅ Format code using terraform fmt
✅ Commit .tf files, NOT .tfstate
✅ Store state in a remote backend with locking
✅ Use modules to avoid repetition
✅ Protect secrets (NEVER hardcode passwords in .tf files)

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📚 Recommended Resources

Resource	Link
Official Docs	https://developer.hashicorp.com/terraform
Terraform Registry	https://registry.terraform.io
DevOpsSchool Terraform Tutorials	https://www.devopsschool.com/blog/category/terraform
Hands-on Labs	https://learn.hashicorp.com

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🏁 Final Thoughts

Terraform isn’t just an IaC tool — it’s an ecosystem.
Learning to use it well will let you:

• Automate cloud provisioning
• Create reproducible environments
• Build infrastructure pipelines
• Work in real enterprise cloud projects

Treat infrastructure like code, version it, review it, test it — that’s Terraform magic.

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