Terraform.tfvars file - Mini Project: Build & Apply

Using a Terraform.tfvars File for Variable Configuration

📖 Scenario: You are setting up a Terraform project to create cloud infrastructure. You want to keep your variable values separate from your main configuration files for easier management and security.

🎯 Goal: Create a terraform.tfvars file to define variable values for your Terraform project. This file will hold exact values for variables like region, instance_type, and instance_count.

📋 What You'll Learn

Create a terraform.tfvars file with exact variable assignments

Include variables: region, instance_type, and instance_count

Use exact values: region = "us-west-2", instance_type = "t2.micro", instance_count = 3

Ensure the file syntax is valid for Terraform variable files

💡 Why This Matters

🌍 Real World

Terraform.tfvars files are used in real projects to separate variable values from code, making infrastructure easier to manage and update.

💼 Career

Knowing how to use terraform.tfvars files is essential for cloud engineers and DevOps professionals managing infrastructure as code.

1

Create the terraform.tfvars file with the region variable

Create a terraform.tfvars file and add the variable region with the exact value "us-west-2".

Terraform

# Your code here

Hint

Use the format variable_name = "value" in the terraform.tfvars file.

2

Add the instance_type variable to terraform.tfvars

In the terraform.tfvars file, add the variable instance_type with the exact value "t2.micro" below the region variable.

Terraform

region = "us-west-2"
# Your code here

Hint

Add a new line with instance_type = "t2.micro" below the existing region variable.

3

Add the instance_count variable to terraform.tfvars

In the terraform.tfvars file, add the variable instance_count with the exact value 3 below the instance_type variable.

Terraform

region = "us-west-2"
instance_type = "t2.micro"
# Your code here

Hint

Add a new line with instance_count = 3 below the existing variables.

4

Complete the terraform.tfvars file with all variables

Ensure the terraform.tfvars file contains the variables region, instance_type, and instance_count with the exact values "us-west-2", "t2.micro", and 3 respectively.

Terraform

region = "us-west-2"
instance_type = "t2.micro"
instance_count = 3
# Verify all variables are present

Hint

Check that all three variables are present with the exact values.

Practice

1. What is the main purpose of the terraform.tfvars file in a Terraform project?

easy

A. To store Terraform state files

B. To define the Terraform provider configuration

C. To write the main infrastructure resources

D. To store values for variables separately from the main Terraform code

Solution

1. Step 1: Understand the role of terraform.tfvars

   This file is used to provide values for variables declared in Terraform configuration files, keeping values separate from code.

2. Step 2: Differentiate from other files

   Provider configuration and resource definitions are in .tf files, and state files are managed separately, not in terraform.tfvars.

3. Final Answer:

   To store values for variables separately from the main Terraform code -> Option D

4. Quick Check:

   Variable values stored separately = D [OK]

Hint: Remember: tfvars holds variable values, not code or state [OK]

Common Mistakes:

• Confusing tfvars with provider or resource files
• Thinking tfvars stores state files
• Assuming tfvars contains resource definitions

2. Which of the following is the correct syntax to assign a list of strings in a terraform.tfvars file?

easy

A. my_list = {"apple", "banana", "cherry"}

B. my_list = ("apple", "banana", "cherry")

C. my_list = ["apple", "banana", "cherry"]

D. my_list = "apple", "banana", "cherry"

Solution

1. Step 1: Identify list syntax in tfvars

   Terraform uses square brackets [] to define lists in tfvars files.

2. Step 2: Check each option

   my_list = ["apple", "banana", "cherry"] uses square brackets with quoted strings, which is correct. Options B and C use parentheses or curly braces, which are invalid for lists. my_list = "apple", "banana", "cherry" is missing brackets.

3. Final Answer:

   my_list = ["apple", "banana", "cherry"] -> Option C

4. Quick Check:

   Lists use square brackets [] = A [OK]

Hint: Lists always use square brackets [] in tfvars [OK]

Common Mistakes:

• Using parentheses or curly braces instead of square brackets
• Forgetting quotes around string items
• Omitting brackets entirely

3. Given the following terraform.tfvars content:

region = "us-west-2"
instance_count = 3
enable_backup = true
allowed_ips = ["10.0.0.1", "10.0.0.2"]

What is the value and type of enable_backup when accessed in Terraform?

medium

A. String "true"

B. Boolean true

C. Number 1

D. List with one element "true"

Solution

1. Step 1: Identify the value type in tfvars

   The value enable_backup = true is a boolean literal, not a string or number.

2. Step 2: Understand Terraform variable typing

   Terraform reads true as a boolean true, not as a string or number.

3. Final Answer:

   Boolean true -> Option B

4. Quick Check:

   Boolean literals stay boolean = B [OK]

Hint: True/false without quotes are booleans in tfvars [OK]

Common Mistakes:

• Treating true as a string by adding quotes
• Assuming true converts to number 1
• Confusing boolean with list type

4. You wrote this in your terraform.tfvars file:

max_instances = 5
allowed_ports = [80, 443, 22

When running Terraform, you get a syntax error. What is the most likely cause?

medium

A. Missing closing bracket for the list

B. Using numbers instead of strings in the list

C. Variable names cannot have underscores

D. The equals sign should be a colon

Solution

1. Step 1: Check list syntax carefully

   The list allowed_ports is opened with [ but the snippet ends after 22 with no closing ].

2. Step 2: Identify syntax error

   The list lacks a closing bracket, causing the syntax error. Other options are invalid: underscores are allowed, numbers are fine in lists, and = is correct syntax.

3. Final Answer:

   Missing closing bracket for the list -> Option A

4. Quick Check:

   Lists must have matching brackets = C [OK]

Hint: Always count opening and closing brackets in lists [OK]

Common Mistakes:

• Forgetting to close lists with a bracket
• Thinking numbers must be strings
• Using colons instead of equals

5. You want to use a map variable in your Terraform configuration to assign different instance types per environment. Which terraform.tfvars content correctly assigns instance types for "dev" and "prod" environments?

hard

A. instance_types = { dev = "t2.micro", prod = "t2.large" }

B. instance_types = ["dev" = "t2.micro", "prod" = "t2.large"]

C. instance_types = (dev: "t2.micro", prod: "t2.large")

D. instance_types = { "dev", "t2.micro", "prod", "t2.large" }

Solution

1. Step 1: Understand map syntax in tfvars

   Maps use curly braces {} with key = value pairs, keys and values can be strings.

2. Step 2: Evaluate each option

   instance_types = { dev = "t2.micro", prod = "t2.large" } correctly uses curly braces with keys and values separated by =. instance_types = ["dev" = "t2.micro", "prod" = "t2.large"] uses square brackets and equals inside, which is invalid. instance_types = (dev: "t2.micro", prod: "t2.large") uses parentheses and colons, invalid syntax. instance_types = { "dev", "t2.micro", "prod", "t2.large" } uses curly braces but with commas separating keys and values without equals, invalid.

3. Final Answer:

   instance_types = { dev = "t2.micro", prod = "t2.large" } -> Option A

4. Quick Check:

   Maps use curly braces with key = value pairs = A [OK]

Hint: Maps use curly braces with key = value pairs in tfvars [OK]

Common Mistakes:

• Using square brackets for maps
• Using colons instead of equals
• Separating keys and values with commas only