Terraform.tfvars file - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Configuration

intermediate

Identify the correct value of a variable from a Terraform.tfvars file

Given the following Terraform.tfvars content, what is the value of the variable instance_count after Terraform applies the configuration?

Terraform

instance_count = 3
region = "us-west-2"
instance_type = "t2.micro"

A 3

B us-west-2

C t2.micro

D null

💡 Hint

Look for the variable name and its assigned value in the tfvars content.

The variable instance_count is assigned the value 3 in the Terraform.tfvars file, so Terraform uses this value during deployment.

❓ service_behavior

intermediate

Effect of missing variable in Terraform.tfvars file

If a variable db_password is declared in Terraform but not set in the Terraform.tfvars file or elsewhere, what will happen when you run terraform apply?

Terraform

variable "db_password" {
  type = string
  description = "The database password"
}

A Terraform will automatically generate a random password

B Terraform will prompt for the value during apply

C Terraform will use an empty string as the value

D Terraform will fail with a syntax error

💡 Hint

Think about how Terraform handles variables without default values and no input.

Terraform prompts the user to enter a value for variables that have no default and are not set in any input files like tfvars.

❓ Architecture

advanced

Choosing the right Terraform.tfvars file for multiple environments

You have two Terraform.tfvars files: dev.tfvars and prod.tfvars. How do you apply the Terraform configuration for the production environment using the correct tfvars file?

A terraform apply -var-file=prod.tfvars

B terraform apply -var prod.tfvars

C terraform apply --tfvars=prod.tfvars

D terraform apply -config=prod.tfvars

💡 Hint

Check the Terraform CLI option to specify a variable file.

The correct CLI option to specify a variable file is -var-file. This tells Terraform to load variables from the given file.

❓ security

advanced

Best practice for sensitive data in Terraform.tfvars files

Which practice is best to keep sensitive data like passwords secure when using Terraform.tfvars files?

A Encrypt the Terraform.tfvars file and commit the encrypted file to version control

B Store sensitive values in Terraform.tfvars and commit the file to version control

C Use environment variables or secret management tools instead of storing sensitive data in Terraform.tfvars

D Write sensitive data directly in Terraform configuration files

💡 Hint

Think about how to avoid exposing secrets in code repositories.

Storing sensitive data in environment variables or secret managers avoids exposing secrets in files that might be committed to version control.

🧠 Conceptual

expert

Understanding variable precedence with Terraform.tfvars

Given a variable region defined with a default in Terraform, set to "us-east-1", and also set in terraform.tfvars as "us-west-2", and finally set via CLI as -var='region=eu-central-1', what value will Terraform use for region?

Terraform

variable "region" {
  type = string
  default = "us-east-1"
}

A us-east-1

B us-west-2

C Terraform will raise an error due to conflicting values

D eu-central-1

💡 Hint

Remember the order of precedence for variable values in Terraform.

Terraform uses CLI -var values first, then tfvars files, then defaults. So CLI value eu-central-1 overrides others.

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