Environment variables (TF_VAR_) in Terraform - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to reference the environment variable for the Terraform variable 'region'.

Terraform

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

provider "aws" {
  region = var.[1]
}

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

AAWS_REGION

Bregion

CTF_VAR_region

Denv_region

Attempts:

3 left

💡 Hint

Common Mistakes

Using the environment variable name directly in the code.

Confusing environment variable names with Terraform variable names.

The Terraform variable is accessed using var.region. The environment variable TF_VAR_region sets this variable but is not used directly in code.

2fill in blank

medium

Complete the command to set the environment variable for Terraform variable 'instance_type' in Linux shell.

Terraform

export [1]="t2.micro"

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

Ainstance_type

Bterraform_instance_type

CAWS_INSTANCE_TYPE

DTF_VAR_instance_type

Attempts:

3 left

💡 Hint

Common Mistakes

Setting environment variable without the TF_VAR_ prefix.

Using unrelated environment variable names.

Terraform reads variables from environment variables prefixed with TF_VAR_. So to set instance_type, use TF_VAR_instance_type.

3fill in blank

hard

Fix the error in the Terraform variable declaration to use a default value from environment variable 'TF_VAR_bucket_name'.

Terraform

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

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

A"my-default-bucket"

Bvar.TF_VAR_bucket_name

Cnull

Denv("TF_VAR_bucket_name")

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to call environment functions inside variable defaults.

Using variable names with TF_VAR_ prefix inside Terraform code.

Terraform does not support using environment variables directly inside variable defaults. The default must be a literal or expression. Environment variables set TF_VAR_bucket_name externally.

4fill in blank

hard

Fill both blanks to correctly use a variable 'ami_id' set via environment variable and reference it in resource.

Terraform

variable "ami_id" {
  type = string
}

resource "aws_instance" "example" {
  ami           = var.[1]
  instance_type = "t2.micro"
  tags = {
    Name = "ExampleInstance"
  }
  lifecycle {
    ignore_changes = ["[2]"]
  }
}

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

Aami_id

Bami

Ctags

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong variable names in references.

Not quoting attribute names in ignore_changes.

The variable is named ami_id and referenced as var.ami_id. The lifecycle block ignores changes to the ami_id attribute to prevent recreation.

5fill in blank

hard

Fill all three blanks to create a Terraform variable 'env' with default from environment variable, use it in provider, and output it.

Terraform

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

provider "aws" {
  region = var.[2]
}

output "environment" {
  value = var.[3]
}

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

Adev

Benv

Dregion

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing variable names with environment variable names.

Using region instead of env in provider or output.

The variable env has a default value (e.g., "dev") which can be overridden by the environment variable TF_VAR_env. The provider uses var.env if it expects environment name, and the output shows var.env.

Practice

1. What is the purpose of using environment variables with the TF_VAR_ prefix in Terraform?

easy

A. To set Terraform input variables without hardcoding them in configuration files

B. To define backend storage for Terraform state files

C. To specify the Terraform provider version

D. To enable debugging output during Terraform runs

Solution

1. Step 1: Understand Terraform variable usage

   Terraform variables allow customization of configurations without changing code files.

2. Step 2: Role of TF_VAR_ prefix

   Environment variables prefixed with TF_VAR_ automatically set Terraform input variables, keeping code clean and secure.

3. Final Answer:

   To set Terraform input variables without hardcoding them in configuration files -> Option A

4. Quick Check:

   Environment variables with TF_VAR_ prefix set variables [OK]

Hint: TF_VAR_ prefix sets Terraform variables via environment [OK]

Common Mistakes:

• Confusing TF_VAR_ with backend configuration
• Using TF_VAR_ to set provider versions
• Expecting TF_VAR_ to enable debug logs

2. Which of the following is the correct way to set a Terraform variable named region using an environment variable?

easy

A. TF_VARregion=us-west-2

B. set TF_VAR-region=us-west-2

C. export TF_VAR_region=us-west-2

D. terraform var region=us-west-2

Solution

1. Step 1: Identify correct environment variable syntax

   Terraform expects environment variables for variables to be prefixed with TF_VAR_ followed by the variable name.

2. Step 2: Correct shell export command

   In Unix-like shells, export TF_VAR_region=us-west-2 correctly sets the variable.

3. Final Answer:

   export TF_VAR_region=us-west-2 -> Option C

4. Quick Check:

   Use export TF_VAR_variable=value [OK]

Hint: Use export TF_VAR_variable=value to set variables [OK]

Common Mistakes:

• Using dash instead of underscore in TF_VAR_ prefix
• Missing export keyword in Unix shell
• Trying to set variables with terraform command directly

3. Given the Terraform variable declaration:

variable "instance_type" { default = "t2.micro" }

and the environment variable set as export TF_VAR_instance_type=t3.medium, what will be the value of var.instance_type during Terraform apply?

medium

A. "t2.micro" (default value)

B. "t3.medium" (from environment variable)

C. null (no value set)

D. Error: variable instance_type not set

Solution

1. Step 1: Understand variable precedence

   Terraform uses environment variables with TF_VAR_ prefix to override default variable values.

2. Step 2: Apply environment variable value

   Since TF_VAR_instance_type is set to "t3.medium", this value overrides the default "t2.micro".

3. Final Answer:

   "t3.medium" (from environment variable) -> Option B

4. Quick Check:

   Environment variable overrides default value [OK]

Hint: Environment variable overrides default Terraform variable [OK]

Common Mistakes:

• Assuming default always applies ignoring environment variable
• Expecting error if environment variable is set
• Confusing null with default value

4. You set the environment variable TF_VAR_count=3 but Terraform still uses the default value count = 1 from the variable declaration. What is the most likely cause?

medium

A. The environment variable name is case-sensitive and should be TF_VAR_Count

B. The environment variable was set after running terraform init

C. The variable count is declared as a string, but environment variable is numeric

D. The shell session where Terraform runs does not have the environment variable exported

Solution

1. Step 1: Check environment variable visibility

   Terraform reads environment variables from the shell session it runs in; if not exported, Terraform won't see it.

2. Step 2: Confirm export of variable

   Setting TF_VAR_count=3 without export means it's not passed to child processes like Terraform.

3. Final Answer:

   The shell session where Terraform runs does not have the environment variable exported -> Option D

4. Quick Check:

   Environment variables must be exported to be visible [OK]

Hint: Always export environment variables before running Terraform [OK]

Common Mistakes:

• Assuming variable names are case-insensitive
• Thinking terraform init caches variable values
• Confusing variable type mismatch as cause

5. You want to securely provide a sensitive variable db_password to Terraform without storing it in code or plain text files. Which approach using environment variables is best practice?

hard

A. Set export TF_VAR_db_password=your_password in your shell before running Terraform

B. Hardcode the password in terraform.tfvars file

C. Use terraform apply -var 'db_password=your_password' every time

D. Store the password in a public GitHub repository and reference it

Solution

1. Step 1: Avoid storing sensitive data in code files

   Hardcoding passwords in files or public repos risks exposure.

2. Step 2: Use environment variables for sensitive data

   Setting TF_VAR_db_password in the shell keeps secrets out of code and version control.

3. Final Answer:

   Set export TF_VAR_db_password=your_password in your shell before running Terraform -> Option A

4. Quick Check:

   Environment variables keep secrets out of code [OK]

Hint: Use TF_VAR_ environment variables to keep secrets out of code [OK]

Common Mistakes:

• Storing secrets in terraform.tfvars files
• Passing secrets on command line risking history leaks
• Publishing secrets in public repositories