Demo Variables

Welcome to this hands-on lab on defining and using variables in Terraform (OpenTofu). By the end of this tutorial, you’ll understand how to declare different variable types, fetch elements from maps and lists, and refactor resources to leverage variables for cleaner, reusable configurations.

1. Variable Type Quiz

Question: Which of the following is not a valid Terraform variable type?

object
item
tuple
list
map

Answer: item is not a valid variable type in Terraform/OpenTofu.

Variable Type	Description
object	Collection of named attributes with specific types
tuple	Ordered list of elements with potentially different types
list	Ordered homogeneous collection
map	Unordered key–value pairs with homogeneous values

For more details, see the Terraform Variable Types.

2. Data Type Quiz

Question: Which of the following is not a valid data type in OpenTofu?

list
tuple
map
array
set

Answer: array is not a valid data type in OpenTofu.

Setup: Navigate to the Variables Directory

cd /root/OpenTofu-project/variables

3. Inspecting `number`

Open variables.tf and locate:

variable "number" {
  type    = bool
  default = false
}

Question: Which type does number belong to?
Answer: It’s a boolean.

4. Fetching a Map Value

In variables.tf, you have:

variable "hard_drive" {
  type = map(string)
  default = {
    slow = "HDD"
    fast = "SSD"
  }
}

Question: How do you retrieve the "slow" entry?

var.hard_drive["slow"]

You can also use the dot notation if your key is a valid identifier, e.g., var.hard_drive.slow.

5. List Indexing

Definition in variables.tf:

variable "gender" {
  type    = list(string)
  default = ["Male", "Female"]
}

Lists are zero-indexed.
"Male" → index 0
"Female" → index 1

Answer: The index of "Female" is 1.

6. Identifying a Set Definition Error

variable "users" {
  type    = set(string)
  default = ["tom", "jerry", "pluto", "daffy", "donald", "jerry"]
}

Type: set(string)
Mistake: Sets must not contain duplicates; "jerry" appears twice.

Defining duplicate elements in a set will cause validation errors. Ensure each member is unique.

7. Inspecting a Resource Block

In main.tf, you added:

resource "local_file" "jedi" {
  filename = "/root/first-jedi"
  content  = "phanius"
}

Question: What is the value of the content argument?
Answer: "phanius"

8. Refactoring to Use Variables

Declare a map variable in variables.tf:

variable "jedi" {
  type = map(string)
  default = {
    filename = "/root/first-jedi"
    content  = "phanius"
  }
}

Update the resource in main.tf:

resource "local_file" "jedi" {
  filename = var.jedi["filename"]
  content  = var.jedi["content"]
}

This makes your configuration more modular and easier to maintain.

9. Initialize, Plan, and Apply

cd /root/OpenTofu-project/variables
opentofu init
opentofu plan

Expected output snapshot:

+ resource "local_file" "jedi" {
    + content     = "phanius"
    + filename    = "/root/first-jedi"
    ...
  }

Plan: 1 to add, 0 to change, 0 to destroy.

Apply the changes:

opentofu apply
# Confirm with "yes"

After success:

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

Verify the file:

cat /root/first-jedi
# phanius

That’s it for this lab. Thank you for following along!

Course Introduction

Introduction to Infrastructure as Code

OpenTofu Basics

OpenTofu State

Working with OpenTofu

Remote State

OpenTofu Provisioners

OpenTofu Import, Tainting Resources and Deubugging

OpenTofu Modules

OpenTofu Functions and Conditional Expressions

OpenTofu: Beyond Basics

Course Conclusion

Getting Started with OpenTofu

1. Variable Type Quiz

2. Data Type Quiz

Setup: Navigate to the Variables Directory

3. Inspecting `number`

4. Fetching a Map Value

5. List Indexing

6. Identifying a Set Definition Error

7. Inspecting a Resource Block

8. Refactoring to Use Variables

9. Initialize, Plan, and Apply

Links and References

Watch Video

Practice Lab

​1. Variable Type Quiz

​2. Data Type Quiz

​Setup: Navigate to the Variables Directory

​3. Inspecting number

​4. Fetching a Map Value

​5. List Indexing

​6. Identifying a Set Definition Error

​7. Inspecting a Resource Block

​8. Refactoring to Use Variables

​9. Initialize, Plan, and Apply

​Links and References

Watch Video

Practice Lab

1. Variable Type Quiz

2. Data Type Quiz

Setup: Navigate to the Variables Directory

3. Inspecting `number`

4. Fetching a Map Value

5. List Indexing

6. Identifying a Set Definition Error

7. Inspecting a Resource Block

8. Refactoring to Use Variables

9. Initialize, Plan, and Apply

Links and References