Module inputs (variables) in Terraform - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a variable named 'region' with a default value.

Terraform

variable "region" {
  type    = string
  default = "[1]"
}

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

Aus-west-2

B123

Ctrue

D[]

Attempts:

3 left

💡 Hint

Common Mistakes

Using a boolean or number instead of a string for the default value.

Leaving the default value empty.

The variable 'region' is declared as a string with a default value 'us-west-2'.

2fill in blank

medium

Complete the code to pass the variable 'region' to the module input.

Terraform

module "network" {
  source = "./modules/network"
  region = [1]
}

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

A"us-east-1"

Bmodule.region

Cregion

Dvar.region

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the variable name without 'var.' prefix.

Passing a string literal instead of the variable.

To pass a variable to a module input, use the syntax var.variable_name.

3fill in blank

hard

Fix the error in the variable declaration by completing the type definition.

Terraform

variable "instance_count" {
  type = [1]
  default = 3
}

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

Anumber

Bbool

Clist

Dstring

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'string' type for a numeric default value.

Using 'bool' or 'list' which do not match the default.

The variable 'instance_count' holds a number, so its type should be 'number'.

4fill in blank

hard

Fill both blanks to declare a variable 'tags' as a map of strings with a default.

Terraform

variable "tags" {
  type    = map[1]string[2]
  default = {
    Environment = "dev"
  }
}

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

A(

B[

C)

D]

Attempts:

3 left

💡 Hint

Common Mistakes

Using square brackets instead of parentheses.

Omitting one of the brackets.

Maps in Terraform are declared with map(string) using parentheses.

5fill in blank

hard

Fill all three blanks to pass variables 'region', 'instance_count', and 'tags' to the module.

Terraform

module "app" {
  source         = "./modules/app"
  region         = [1]
  instance_count = [2]
  tags           = [3]
}

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

Avar.region

Bvar.instance_count

Cvar.tags

Dmodule.region

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'module.' prefix instead of 'var.'.

Passing variable names without 'var.' prefix.

Module inputs are assigned using variables with the 'var.' prefix.

Practice

1. What is the main purpose of using variables in a Terraform module?

easy

A. To customize module behavior without changing its code

B. To store sensitive data only

C. To define output values from the module

D. To create resources automatically

Solution

1. Step 1: Understand module customization

   Variables allow users to provide input values to modules, changing how they behave without editing the module code itself.

2. Step 2: Differentiate variables from other features

   Variables are not for outputs or automatic resource creation; they are inputs to customize modules.

3. Final Answer:

   To customize module behavior without changing its code -> Option A

4. Quick Check:

   Module inputs = customization [OK]

Hint: Variables customize modules without code edits [OK]

Common Mistakes:

• Confusing variables with outputs
• Thinking variables create resources
• Assuming variables only store secrets

2. Which of the following is the correct syntax to declare a string variable named region with a default value of us-west-1?

easy

A. variable "region" = "us-west-1"

B. variable region { type = "string" default = us-west-1 }

C. variable "region" { default = us-west-1 type = string }

D. variable "region" { type = string default = "us-west-1" }

Solution

1. Step 1: Check variable block syntax

   Terraform variables use the syntax: variable "name" { type = string default = "value" } with quotes around strings.

2. Step 2: Validate variable "region" { type = string default = "us-west-1" }

   correctly uses quotes for the variable name and default string value, and sets type properly.

3. Final Answer:

   variable "region" { type = string default = "us-west-1" } -> Option D

4. Quick Check:

   Correct variable block syntax = variable "region" { type = string default = "us-west-1" } [OK]

Hint: Use quotes for names and string defaults in variable blocks [OK]

Common Mistakes:

• Missing quotes around strings
• Wrong order of attributes
• Assigning variable directly without block

3. Given this module variable declaration:

variable "instance_count" {
  type    = number
  default = 2
}

And this usage inside the module:

resource "aws_instance" "example" {
  count = var.instance_count
  ami           = "ami-123456"
  instance_type = "t2.micro"
}

What will happen if the module is called without specifying instance_count?

medium

A. Only one instance will be created

B. Two AWS instances will be created

C. An error occurs because instance_count is missing

D. No instances will be created

Solution

1. Step 1: Understand default variable behavior

   If a variable has a default value and is not overridden, Terraform uses the default.

2. Step 2: Apply default to resource count

   The count argument uses var.instance_count, which defaults to 2, so two instances are created.

3. Final Answer:

   Two AWS instances will be created -> Option B

4. Quick Check:

   Default variable value used = 2 instances [OK]

Hint: Default variable values apply if no input given [OK]

Common Mistakes:

• Assuming missing variable causes error
• Thinking default is ignored
• Confusing count with instance_type

4. You have this variable declaration inside a module:

variable "env" {
  type = string
}

When calling the module, you forget to provide a value for env. What will happen?

medium

A. Terraform will throw an error about missing required variable

B. Terraform will use an empty string as default

C. Terraform will assign null automatically

D. Terraform will use the string "env" as default

Solution

1. Step 1: Check variable declaration for default

   The variable env has no default value, so it is required.

2. Step 2: Understand Terraform behavior on missing required variables

   If a required variable is not provided, Terraform throws an error and stops.

3. Final Answer:

   Terraform will throw an error about missing required variable -> Option A

4. Quick Check:

   Required variable missing = error [OK]

Hint: No default means variable is required [OK]

Common Mistakes:

• Assuming empty string or null is automatic default
• Thinking Terraform guesses a value
• Confusing variable name with default

5. You want to create a reusable module that accepts a list of subnet IDs as input. Which variable declaration correctly enforces that the input must be a list of strings and has no default value?

hard

A. variable "subnet_ids" { type = string default = [] }

B. variable "subnet_ids" { type = list number default = ["subnet-123"] }

C. variable "subnet_ids" { type = list(string) }

D. variable "subnet_ids" { type = list(string) default = null }

Solution

1. Step 1: Identify correct type syntax for list of strings

   Terraform uses list(string) to specify a list where each item is a string.

2. Step 2: Check default value presence

   No default means the variable is required. variable "subnet_ids" { type = list(string) } has no default, so input must be provided.

3. Final Answer:

   variable "subnet_ids" { type = list(string) } -> Option C

4. Quick Check:

   List of strings required, no default = variable "subnet_ids" { type = list(string) } [OK]

Hint: Use type = list(string) and omit default to require input [OK]

Common Mistakes:

• Using wrong type like string instead of list(string)
• Providing default empty list when input should be required
• Using invalid syntax for type or default