opentofu_cheatsheet.md

OpenTofu Cheatsheet

OpenTofu is an open-source infrastructure as code tool that lets you define both cloud and on-prem resources in human-readable configuration files that you can version, reuse, and share.

Core Concepts

• Provider: Plugin that OpenTofu uses to interact with cloud providers, SaaS providers, and other APIs
• Resource: A component of your infrastructure (e.g., virtual machine, database)
• Module: Reusable container for multiple resources that are used together
• State: OpenTofu's record of all managed resources and their properties
• Variables: Parameters for configuring your infrastructure
• Outputs: Return values from your infrastructure

Basic Commands

Command	Description
tofu init	Initialize a working directory containing configuration files
tofu plan	Create an execution plan to preview changes
tofu apply	Apply the changes required to reach the desired state
tofu destroy	Destroy all resources managed by the current configuration
tofu validate	Validate configuration files
tofu fmt	Reformat configuration files to canonical style
tofu show	Show the current state or a saved plan
tofu state list	List resources in the state file
tofu output	Show output values from the state file

Configuration Basics

Provider Configuration

provider "aws" {
  region = "us-east-1"
}

Resource Definition

resource "aws_instance" "example" {
  ami           = "ami-0c55b159cbfafe1f0"
  instance_type = "t2.micro"
  
  tags = {
    Name = "example-instance"
  }
}

Variables

# In variables.tf
variable "instance_type" {
  description = "The type of EC2 instance to launch"
  type        = string
  default     = "t2.micro"
}

# Usage in main.tf
resource "aws_instance" "example" {
  instance_type = var.instance_type
  # ...
}

Outputs

output "instance_ip" {
  description = "The public IP of the instance"
  value       = aws_instance.example.public_ip
}

Common Workflows

Initialize and Apply Changes

# Initialize the directory
tofu init

# Create and review a plan
tofu plan

# Apply changes
tofu apply

Working with State

# List resources in state
tofu state list

# Show details of a specific resource
tofu state show aws_instance.example

# Remove a resource from state (without destroying it)
tofu state rm aws_instance.example