Installing OpenTofu and HashiCorp Configuraton Language HCL Basics

In this lesson, you’ll learn how to install OpenTofu—the community-driven fork of Terraform—and get up to speed with writing configuration files in HashiCorp Configuration Language (HCL). We’ll cover:

• Installing the tofu CLI
• Writing HCL .tf files
• Examples for local and AWS resources
• A step-by-step OpenTofu workflow

Table of Contents

• Installing OpenTofu
• HCL Configuration Files
  • Example: Managing Local Files
• AWS Resource Examples
• What Is a Resource?
• OpenTofu Workflow
  1. Initialize the Directory
  2. Preview the Execution Plan
  3. Apply the Changes
  4. Verify and Inspect
• Viewing Resource Arguments
• Links and References

Installing OpenTofu

OpenTofu ships as a single binary. Download the appropriate archive for your OS, unpack it, and move tofu into your system PATH:

wget https://github.com/opentofu/opentofu/releases/download/v1.6.1/tofu_1.6.1_linux_amd64.zip
unzip tofu_1.6.1_linux_amd64.zip
mv tofu /usr/local/bin/
tofu version

Expected output:

OpenTofu v1.6.1
on linux_amd64

You’re now ready to write HCL configuration files and provision resources.

HCL Configuration Files

HCL .tf files consist of blocks (grouping of settings) and arguments (key-value pairs) that define the desired state of your infrastructure.

Example: Managing Local Files

Create local.tf to manage a simple text file:

resource "local_file" "pet" {
  filename = "/root/pets.txt"
  content  = "We love pets!"
}

• resource: Block type
• "local_file": Provider local, resource file
• "pet": Logical name
• Inside {}: Arguments like filename and content

AWS Resource Examples

HCL syntax stays consistent across providers. Here are two common AWS examples:

EC2 Instance

resource "aws_instance" "web" {
  ami           = "ami-0c2f25c1f66a1ff4d"
  instance_type = "t2.micro"
}

S3 Bucket

resource "aws_s3_bucket" "data" {
  bucket = "webserver-bucket-org-2207"
  acl    = "private"
}

What Is a Resource?

A resource is any object OpenTofu manages—either locally or in the cloud. Examples include:

OpenTofu Workflow

Provisioning with OpenTofu follows four main steps:

1. Write your HCL configuration files.
2. Initialize with tofu init.
3. Review changes using tofu plan.
4. Apply changes via tofu apply.

1. Initialize the Directory

tofu init

Output:

Initializing the backend...

Initializing provider plugins...
- Finding latest version of hashicorp/local...
- Installing hashicorp/local v2.4.1...
- Installed hashicorp/local v2.4.1 (signed, key ID 0C0AF313E5FD9F80)

Providers are signed by their developers.
If you'd like to know more about provider signing, see:
  https://opentofu.org/docs/cli/plugins/signing/

A lock file (.terraform.lock.hcl) has been created. Commit it to version control.
OpenTofu has been successfully initialized!

2. Preview the Execution Plan

tofu plan

+ resource "local_file" "pet" {
    + filename = "/root/pets.txt"
    + content  = "We love pets!"
}
Plan: 1 to add, 0 to change, 0 to destroy.

3. Apply the Changes

tofu apply

OpenTofu will perform the following actions:
  + resource "local_file" "pet" {
      + content              = "We love pets!"
      + filename             = "/root/pets.txt"
      + id                   = (known after apply)
    }

Plan: 1 to add, 0 to change, 0 to destroy.
Enter a value: yes

local_file.pet: Creating...
local_file.pet: Creation complete after 0s [id=cba595b7d9f94ba…]
Apply complete! Resources: 1 added, 0 changed, 0 destroyed.

tofu apply -auto-approve

4. Verify and Inspect

cat /root/pets.txt
tofu show local_file.pet
# (Displays state details)

Viewing Resource Arguments

Each resource has required and optional arguments. Consult the provider’s official docs to discover available fields. For example, the local provider’s local_file resource lists filename as required, with optional settings like directory_permission.

That’s it for this lesson! Next, we’ll dive into updating and destroying resources with OpenTofu.

Links and References

• OpenTofu CLI Documentation
• HashiCorp Configuration Language (HCL) Spec
• Registry: hashicorp/local
• AWS Provider Docs