Terraform Usage#

This document provides a guide to using Terraform for managing infrastructure as code, including version management with tfenv.

Overview#

Terraform is an open-source infrastructure as code (IaC) software tool that enables you to safely and predictably create, change, and improve infrastructure. It codifies APIs into declarative configuration files.

tfenv is a Terraform version manager, allowing you to easily switch between different versions of Terraform on a per-project basis.

Installation#

`tfenv` (Terraform Version Manager)#

It's recommended to install tfenv first to manage your Terraform versions.

Installation (macOS with Homebrew):

brew install tfenv

For other installation methods (e.g., Git clone), refer to the tfenv installation guide.

Post-installation: Ensure tfenv is added to your shell's PATH. If installed via Homebrew, this is usually handled automatically. Otherwise, you might need to add $(brew --prefix tfenv)/bin (or the equivalent for your installation method) to your PATH.

Terraform (via `tfenv`)#

Once tfenv is installed, you can install specific Terraform versions:

List available Terraform versions:
```
tfenv list-remote
```

Install a specific version:

tfenv install <version>
# Example: tfenv install 1.0.0

To install the latest stable version:

tfenv install latest

Select a Terraform version to use:
- Globally:
```
tfenv use <version>
# Example: tfenv use 1.0.0
```
- Per project (recommended): Create a .terraform-version file in your project's root directory containing the desired version number:
```
# .terraform-version
1.0.0
```
  tfenv will automatically pick up this version when you cd into the directory.

Verify installation:

terraform --version
which terraform # Should point to a tfenv shim

Basic Terraform Workflow#

Terraform commands are typically run within a directory containing your .tf configuration files.

terraform init: Initializes a working directory containing Terraform configuration files. This is the first command that should be run after writing a new Terraform configuration or cloning an existing one.
```
terraform init
```
This command also initializes backend configuration (for state storage) and downloads provider plugins.
terraform plan: Creates an execution plan. Terraform performs a refresh, unless explicitly disabled, and then determines what actions are necessary to achieve the desired state specified in the configuration files.
```
terraform plan
# Save the plan to a file:
# terraform plan -out=tfplan
```
This is a good way to check whether the proposed changes match your expectations before applying them.

terraform apply: Applies the changes required to reach the desired state of the configuration, or the pre-determined changes if a plan file is provided.

terraform apply
# Apply a saved plan (prompts for confirmation):
# terraform apply tfplan
# Auto-approve (use with caution):
# terraform apply -auto-approve
# Or apply a saved plan without prompting:
# terraform apply -auto-approve tfplan

terraform destroy: Destroys all remote objects managed by a particular Terraform configuration.
```
terraform destroy
```
Use with extreme caution, as this will remove your managed infrastructure.

Common Terraform Commands#

terraform fmt: Rewrites Terraform configuration files to a canonical format and style.
```
terraform fmt
# Check for formatting issues: terraform fmt -check
```
terraform validate: Validates the syntax and arguments of configuration files.
```
terraform validate
```
terraform output: Reads an output variable from a Terraform state file.
```
terraform output <output_variable_name>
```
terraform state list: Lists resources within a Terraform state file.
```
terraform state list
```
terraform workspace list/select/new/delete: Manages Terraform workspaces for different environments (e.g., dev, staging, prod).

Resources#

Official Terraform Documentation: https://developer.hashicorp.com/terraform/docs
Terraform CLI Commands: https://developer.hashicorp.com/terraform/cli/commands
tfenv GitHub Repository: https://github.com/tfutils/tfenv
Terraform Registry (Providers & Modules): https://registry.terraform.io/

This document provides fundamental guidance. Terraform is a comprehensive tool; always refer to the official documentation for detailed information and best practices.