Creating a child module in Terraform - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to call a child module named 'network'.

Terraform

module "network" {
  source = [1]
}

Drag options to blanks, or click blank then click option'

A"../network"

B"network-module"

C"./modules/network"

D"network"

Attempts:

3 left

💡 Hint

Common Mistakes

Using just the module name without a path.

Using a relative path that does not exist.

The source attribute specifies the path to the child module directory. Using "./modules/network" correctly points to the child module folder.

2fill in blank

medium

Complete the code to pass a variable 'region' with value 'us-west-1' to the child module.

Terraform

module "network" {
  source = "./modules/network"
  [1] = "us-west-1"
}

Drag options to blanks, or click blank then click option'

Aregion

Barea

Czone

Dlocation

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong variable name like 'location' or 'zone'.

Forgetting to pass the variable at all.

The variable name must match the input variable defined in the child module. Here, region is the correct variable to pass.

3fill in blank

hard

Fix the error in the child module call by completing the missing attribute to output the module's VPC ID.

Terraform

output "vpc_id" {
  value = module.network.[1]
}

Drag options to blanks, or click blank then click option'

Avpcid

BvpcId

CvpcID

Dvpc_id

Attempts:

3 left

💡 Hint

Common Mistakes

Using camelCase or incorrect casing.

Using a name not defined in the child module outputs.

The output attribute must exactly match the output name defined in the child module, which is vpc_id in snake_case.

4fill in blank

hard

Fill both blanks to define a child module with source path and pass a variable 'cidr_block'.

Terraform

module "vpc" {
  source = [1]
  [2] = "10.0.0.0/16"
}

Drag options to blanks, or click blank then click option'

A"./modules/vpc"

Bcidr_block

Cvpc_cidr

D"vpc-module"

Attempts:

3 left

💡 Hint

Common Mistakes

Using an incorrect source path.

Using a wrong variable name like 'vpc_cidr'.

The source must point to the child module folder "./modules/vpc". The variable name cidr_block matches the expected input variable in the child module.

5fill in blank

hard

Fill all three blanks to define a child module, pass variables 'name' and 'environment', and output the module's subnet ID.

Terraform

module "subnet" {
  source      = [1]
  name        = [2]
  environment = [3]
}

output "subnet_id" {
  value = module.subnet.subnet_id
}

Drag options to blanks, or click blank then click option'

A"./modules/subnet"

B"prod-subnet"

C"production"

D"./subnet-module"

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect source paths.

Passing variables without quotes.

Using inconsistent variable names.

The source points to the child module folder "./modules/subnet". The variables name and environment are passed with appropriate string values matching typical naming conventions.

Practice

1. What is the main purpose of creating a child module in Terraform?

easy

A. To avoid using variables in Terraform

B. To break down infrastructure into smaller, reusable pieces

C. To increase the number of resources in the root module

D. To deploy resources only in one cloud provider

Solution

1. Step 1: Understand module purpose

   Child modules help organize infrastructure by splitting it into smaller parts.

2. Step 2: Identify benefits

   This makes code reusable and easier to manage across projects.

3. Final Answer:

   To break down infrastructure into smaller, reusable pieces -> Option B

4. Quick Check:

   Child modules = reusable infrastructure parts [OK]

Hint: Child modules = smaller reusable parts of infrastructure [OK]

Common Mistakes:

• Thinking child modules increase resource count in root
• Believing child modules remove need for variables
• Assuming child modules limit to one cloud provider

2. Which Terraform block correctly includes a child module located in the folder ./modules/network?

easy

A. variable "network" { source = "./modules/network" }

B. resource "network" { source = "./modules/network" }

C. provider "network" { source = "./modules/network" }

D. module "network" { source = "./modules/network" }

Solution

1. Step 1: Identify correct block type

   Child modules are included using the module block in Terraform.

2. Step 2: Check syntax for source

   The source attribute points to the child module folder path.

3. Final Answer:

   module "network" { source = "./modules/network" } -> Option D

4. Quick Check:

   Use module block with source path [OK]

Hint: Use module block with source path to include child module [OK]

Common Mistakes:

• Using resource or provider blocks instead of module
• Placing source inside resource or variable blocks
• Incorrect block type for including modules

3. Given this root module code:

module "web" {
  source = "./modules/webserver"
  instance_count = 3
}

And the child module variables.tf contains:

variable "instance_count" {
  type = number
}

What will be the value of var.instance_count inside the child module?

medium

A. 3

B. 0

C. null

D. 1

Solution

1. Step 1: Check variable passing

   The root module passes instance_count = 3 to the child module.

2. Step 2: Confirm variable usage

   The child module declares instance_count variable to receive this value.

3. Final Answer:

   3 -> Option A

4. Quick Check:

   Passed variable value = 3 [OK]

Hint: Passed variable values appear inside child module as given [OK]

Common Mistakes:

• Assuming default or null if variable is declared
• Confusing variable names or missing passing
• Thinking child module variables reset automatically

4. You wrote this root module code:

module "db" {
  source = "./modules/database"
  db_name = "prod"
}

But Terraform shows an error: An argument named "db_name" is not expected here. Did you mean to define a variable named "db_name"?
What is the likely cause?

medium

A. Terraform does not support passing variables to modules

B. The source path is incorrect

C. The child module does not declare a variable named db_name

D. The root module must use resource block instead of module

Solution

1. Step 1: Analyze error message

   The error indicates that the argument "db_name" is not expected, which happens when the child module does not declare a variable named "db_name".

2. Step 2: Check child module variables

   If child module does not declare variable "db_name", Terraform cannot accept the passed value.

3. Final Answer:

   The child module does not declare a variable named db_name -> Option C

4. Quick Check:

   Passing undeclared argument causes "not expected" error [OK]

Hint: Declare variables in child module to accept passed values [OK]

Common Mistakes:

• Ignoring variable declaration in child module
• Assuming source path error without checking variables
• Thinking modules can't receive variables

5. You want to create a child module that provisions an AWS S3 bucket with a customizable name and versioning enabled by default. Which of the following variables.tf and main.tf snippets inside the child module is the best practice?

hard

A. variables.tf:variable "bucket_name" { type = string }
variable "versioning" { type = bool, default = true }main.tf:resource "aws_s3_bucket" "bucket" {
bucket = var.bucket_name
versioning {
enabled = var.versioning
}
}

B. variables.tf:variable "bucket_name" { type = string, default = "mybucket" }
variable "versioning" { type = string }main.tf:resource "aws_s3_bucket" "bucket" {
bucket = var.bucket_name
versioning {
enabled = var.versioning
}
}

C. variables.tf:variable "bucket_name" { type = string }
variable "versioning" { type = string, default = "true" }main.tf:resource "aws_s3_bucket" "bucket" {
bucket = var.bucket_name
versioning {
enabled = var.versioning
}
}

D. variables.tf:variable "bucket_name" { type = number }
variable "versioning" { type = bool }main.tf:resource "aws_s3_bucket" "bucket" {
bucket = var.bucket_name
versioning {
enabled = var.versioning
}
}

Solution

1. Step 1: Check variable types and defaults

   Bucket name should be string without default to force user input. Versioning is boolean with default true.

2. Step 2: Validate resource usage

   Resource uses var.bucket_name and var.versioning correctly with boolean type for versioning enabled.

3. Final Answer:

   variables.tf with string and bool (default true), main.tf using these variables correctly -> Option A

4. Quick Check:

   Correct types and defaults = variables.tf:
   

   variable "bucket_name" { type = string }
   variable "versioning" { type = bool, default = true }

   
   main.tf:
   

   resource "aws_s3_bucket" "bucket" {
     bucket = var.bucket_name
     versioning {
       enabled = var.versioning
     }
   }

   [OK]

Hint: Use correct variable types and defaults for best practice [OK]

Common Mistakes:

• Using string type for boolean variables
• Setting wrong default types
• Using number type for bucket name