Module sources (local, registry, git) in Terraform - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a local module source in Terraform?

A local module source is a module stored on your computer or project folder. You use a relative or absolute path to include it in your Terraform configuration.

beginner

How do you specify a registry module source in Terraform?

You specify a registry module source by using the module's name from the Terraform Registry, usually in the format namespace/name/provider. Terraform downloads it automatically.

intermediate

What is the purpose of using a git module source in Terraform?

A git module source lets you use a module stored in a git repository. You provide the git URL, and optionally a branch, tag, or commit to use specific code versions.

beginner

Example: How to reference a local module in Terraform?

Use source = "./modules/my_module" inside the module block to point to a folder named my_module inside a modules directory.

intermediate

What is the syntax to use a git module source with a specific branch?

Use source = "git::https://github.com/user/repo.git?ref=branch-name" to get the module from a specific branch in the git repository.

Which source format is used to include a module stored on your local machine?

A A relative or absolute file path

B A URL to a git repository

C A module name from Terraform Registry

D An HTTP URL to a zip file

Local modules use file paths to point to folders on your computer.

How do you specify a module from the Terraform Registry?

A Using <namespace>/<name>/<provider> format

B Using a path starting with ./ or ../

C Using a git URL with ref parameter

D Using an HTTP URL to a zip archive

Registry modules use the format namespace/name/provider to identify modules.

What does the 'ref' parameter do in a git module source URL?

A Defines the module version in the registry

B Specifies the branch, tag, or commit to use

C Sets the local path for the module

D Indicates the provider for the module

The 'ref' parameter tells Terraform which git branch, tag, or commit to use.

Which of these is a valid git module source URL?

A https://example.com/module.zip

B ./modules/my_module

C git::https://github.com/user/repo.git?ref=v1.0.0

D hashicorp/aws

Git module sources start with 'git::' followed by the repository URL and optional ref.

If you want to use a module stored in a folder named 'network' inside your project, what source do you use?

A network

B git::network

C hashicorp/network/aws

D ./network

Local modules require a relative path starting with './' to specify the folder.

Explain the differences between local, registry, and git module sources in Terraform.

Think about where the module code is stored and how Terraform accesses it.

Describe how to specify a git module source with a specific branch in Terraform.

Remember the URL format and the ref parameter.

Practice

1. What does the source argument specify in a Terraform module block?

easy

A. The location where Terraform finds the module code

B. The version of Terraform to use

C. The cloud provider for the module

D. The output variables of the module

Solution

1. Step 1: Understand the role of source in a module

   The source argument tells Terraform where to get the module code from, such as a local folder, registry, or Git repo.

2. Step 2: Identify what source does not specify

   It does not specify Terraform version, cloud provider, or outputs; those are separate configurations.

3. Final Answer:

   The location where Terraform finds the module code -> Option A

4. Quick Check:

   Module source = module location [OK]

Hint: Remember: source means 'where to get the module' [OK]

Common Mistakes:

• Confusing source with Terraform version
• Thinking source defines outputs
• Assuming source sets cloud provider

2. Which of the following is the correct syntax to use a local module located in a folder named modules/network?

easy

A. module "net" { source = "modules/network" }

B. module "net" { source = "registry/modules/network" }

C. module "net" { source = "git::https://example.com/network.git" }

D. module "net" { source = "network" }

Solution

1. Step 1: Identify local module source syntax

   Local modules use a relative or absolute path as the source. Here, "modules/network" is a relative path.

2. Step 2: Check other options for correctness

   module "net" { source = "registry/modules/network" } uses registry syntax incorrectly; module "net" { source = "git::https://example.com/network.git" } is for Git sources; module "net" { source = "network" } lacks the folder path.

3. Final Answer:

   module "net" { source = "modules/network" } -> Option A

4. Quick Check:

   Local module source = folder path [OK]

Hint: Local modules use folder paths as source [OK]

Common Mistakes:

• Using registry or git syntax for local modules
• Omitting folder path in source
• Confusing source with module name

3. Given this module block:

module "web" {
  source = "git::https://github.com/example/terraform-web.git"
  version = "v1.0.0"
}

What will Terraform do when you run terraform init?

medium

A. Download the module from the local folder named terraform-web

B. Download the module from the Terraform Registry

C. Clone the Git repository at the given URL and checkout version v1.0.0

D. Fail because version is not supported for Git sources

Solution

1. Step 1: Understand Git source syntax in Terraform

   The source starting with "git::" tells Terraform to clone a Git repository from the URL.

2. Step 2: Interpret the version argument with Git sources

   The version here refers to a Git tag or branch to checkout, so Terraform will checkout "v1.0.0" after cloning.

3. Final Answer:

   Clone the Git repository at the given URL and checkout version v1.0.0 -> Option C

4. Quick Check:

   Git source + version = clone and checkout tag [OK]

Hint: Git source means clone repo; version is Git tag/branch [OK]

Common Mistakes:

• Thinking version is Terraform Registry version
• Assuming source is local folder
• Believing version is unsupported for Git

4. You wrote this module block:

module "db" {
  source = "git::https://github.com/example/terraform-db.git"
  version = "1.0.0"
}

When running terraform init, you get an error. What is the likely cause?

medium

A. The module name 'db' is invalid

B. The version should be prefixed with 'v' like 'v1.0.0' to match Git tags

C. The source URL must be a local path for modules

D. Git URLs cannot be used as module sources

Solution

1. Step 1: Check Git tag naming conventions

   Git tags often start with 'v' (e.g., 'v1.0.0'). If the tag is named with 'v', specifying '1.0.0' causes a mismatch.

2. Step 2: Verify other options for errors

   Git URLs are valid sources; local path is not required; module name 'db' is valid.

3. Final Answer:

   The version should be prefixed with 'v' like 'v1.0.0' to match Git tags -> Option B

4. Quick Check:

   Git version tag must match exact Git tag name [OK]

Hint: Match version exactly to Git tag name (often starts with 'v') [OK]

Common Mistakes:

• Omitting 'v' prefix in version for Git tags
• Thinking Git URLs are invalid module sources
• Assuming module names have strict rules

5. You want to reuse a module from the Terraform Registry named hashicorp/aws with version 4.0.0. Which is the correct module block to use?

hard

A. module "aws_module" {
source = "git::https://github.com/hashicorp/aws.git"
version = "4.0.0"
}

B. module "aws_module" {
source = "registry/hashicorp/aws"
version = "4.0.0"
}

C. module "aws_module" {
source = "./hashicorp/aws"
version = "4.0.0"
}

D. module "aws_module" {
source = "hashicorp/aws"
version = "4.0.0"
}

Solution

1. Step 1: Identify Terraform Registry module source syntax

   Modules from the Terraform Registry use the format "namespace/module" as the source, e.g., "hashicorp/aws".

2. Step 2: Check other options for correctness

   module "aws_module" { source = "git::https://github.com/hashicorp/aws.git" version = "4.0.0" } uses Git URL which is incorrect for Registry modules; module "aws_module" { source = "./hashicorp/aws" version = "4.0.0" } uses local path; module "aws_module" { source = "registry/hashicorp/aws" version = "4.0.0" } uses invalid prefix "registry/".

3. Final Answer:

   module "aws_module" { source = "hashicorp/aws" version = "4.0.0" } -> Option D

4. Quick Check:

   Registry modules use "namespace/module" source format [OK]

Hint: Registry modules use "namespace/module" as source [OK]

Common Mistakes:

• Using Git URL for Registry modules
• Adding extra prefixes like 'registry/'
• Using local paths for Registry modules