Why outputs expose useful information in Terraform - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define an output that shows the instance's public IP.

Terraform

output "instance_ip" {
  value = [1]
}

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

Aaws_instance.example.public_ip

Baws_instance.example.private_ip

Caws_instance.example.id

Daws_instance.example.arn

Attempts:

3 left

💡 Hint

Common Mistakes

Using private_ip instead of public_ip.

Using instance ID or ARN which are not IP addresses.

The output should expose the public IP of the instance, which is accessed via public_ip.

2fill in blank

medium

Complete the code to output the database endpoint after creation.

Terraform

output "db_endpoint" {
  value = [1]
}

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

Aaws_db_instance.main.port

Baws_db_instance.main.id

Caws_db_instance.main.address

Daws_db_instance.main.endpoint

Attempts:

3 left

💡 Hint

Common Mistakes

Using the database ID or port instead of the endpoint.

Using an attribute that does not provide connection info.

The endpoint attribute provides the database connection address, which is useful to expose.

3fill in blank

hard

Fix the error in the output block to correctly expose the load balancer DNS name.

Terraform

output "lb_dns" {
  value = aws_lb.example.[1]
}

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

Aname

Bhostname

Cdns_name

Durl

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'name' which is just the resource name.

Using 'hostname' or 'url' which are not valid attributes.

The correct attribute to get the load balancer's DNS name is dns_name.

4fill in blank

hard

Fill both blanks to output the subnet IDs from a list of subnets.

Terraform

output "subnet_ids" {
  value = [for subnet in [1] : subnet.[2]]
}

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

Aaws_subnet.example

Baws_subnet.example.*

Cid

Dsubnet_id

Attempts:

3 left

💡 Hint

Common Mistakes

Using a single resource instead of a list.

Using 'subnet_id' which is not a valid attribute.

To get all subnet IDs, iterate over the list aws_subnet.example.* and extract the id attribute.

5fill in blank

hard

Fill all three blanks to output a map of instance names to their private IPs, filtering only running instances.

Terraform

output "running_instances" {
  value = { for i in [1] : i.[2] => i.[3] if i.instance_state.name == "running" }
}

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

Aaws_instance.all

Btags.Name

Cprivate_ip

Daws_instance.example

Attempts:

3 left

💡 Hint

Common Mistakes

Using a single instance resource instead of a list.

Using incorrect attributes for name or IP.

Not filtering by running state.

This output creates a map from instance names (tags.Name) to their private IPs (private_ip) for instances in the aws_instance.all list that are running.

Practice

1. What is the main purpose of Terraform outputs?

easy

A. To display important information about deployed resources

B. To delete resources automatically

C. To write logs to a file

D. To encrypt all resource data

Solution

1. Step 1: Understand Terraform outputs role

   Outputs are designed to show key details like IP addresses or IDs after deployment.

2. Step 2: Compare with other options

   Deleting resources, logging, or encrypting are not functions of outputs.

3. Final Answer:

   To display important information about deployed resources -> Option A

4. Quick Check:

   Outputs show info = A [OK]

Hint: Outputs reveal resource info after deployment [OK]

Common Mistakes:

• Thinking outputs delete resources
• Confusing outputs with logging
• Assuming outputs encrypt data

2. Which of the following is the correct syntax to define an output named instance_ip in Terraform?

easy

A. output instance_ip = aws_instance.example.private_ip

B. output instance_ip { value: aws_instance.example.private_ip }

C. output "instance_ip" = aws_instance.example.private_ip

D. output "instance_ip" { value = aws_instance.example.private_ip }

Solution

1. Step 1: Recall Terraform output block syntax

   Outputs use the block format: output "name" { value = ... }

2. Step 2: Check each option

   output "instance_ip" { value = aws_instance.example.private_ip } matches correct syntax; others misuse assignment or block format.

3. Final Answer:

   output "instance_ip" { value = aws_instance.example.private_ip } -> Option D

4. Quick Check:

   Correct output block syntax = B [OK]

Hint: Use output "name" { value = ... } format [OK]

Common Mistakes:

• Using equals sign outside block
• Missing quotes around output name
• Using colon instead of equals

3. Given this output block:

output "db_password" {
  value     = aws_db_instance.main.password
  sensitive = true
}

What will happen when you run terraform apply?

medium

A. The password will be hidden and not shown in the output

B. Terraform will throw a syntax error

C. The password will be shown in the output after apply

D. The password will be printed in plain text in logs

Solution

1. Step 1: Understand the sensitive flag effect

   Setting sensitive = true hides the output value from the CLI after apply.

2. Step 2: Analyze options

   The password will be hidden and not shown in the output correctly states the password is hidden; others are incorrect or unsafe.

3. Final Answer:

   The password will be hidden and not shown in the output -> Option A

4. Quick Check:

   sensitive = true hides output = C [OK]

Hint: Use sensitive = true to hide outputs [OK]

Common Mistakes:

• Assuming sensitive outputs always show
• Confusing syntax with errors
• Thinking sensitive outputs print in logs

4. You wrote this output block:

output "web_url" {
  value = aws_instance.web.public_ip
  sensitive = false
}

After running terraform apply, you see no output displayed. What is the likely cause?

medium

A. Terraform outputs never show IP addresses

B. The sensitive flag hides the output even if false

C. The resource aws_instance.web does not exist or is misspelled

D. Outputs must be declared in a separate file

Solution

1. Step 1: Check resource reference correctness

   If the resource name is wrong or missing, output has no value to show.

2. Step 2: Evaluate other options

   Sensitive = false means output shows; outputs can be in any file; IPs do show.

3. Final Answer:

   The resource aws_instance.web does not exist or is misspelled -> Option C

4. Quick Check:

   Wrong resource name = no output = D [OK]

Hint: Check resource names carefully in outputs [OK]

Common Mistakes:

• Believing sensitive=false hides output
• Thinking outputs must be in separate files
• Assuming IPs never show in outputs

5. You want to share the URL of a deployed web app but keep the admin password secret. Which output configuration achieves this?

hard

A. output "app_url" { value = aws_lb.web.dns_name }
output "admin_password" { value = aws_db.admin.password }

B. output "app_url" { value = aws_lb.web.dns_name }
output "admin_password" { value = aws_db.admin.password sensitive = true }

C. output "app_url" { value = aws_lb.web.dns_name sensitive = true }
output "admin_password" { value = aws_db.admin.password }

D. output "app_url" { value = aws_lb.web.dns_name sensitive = true }
output "admin_password" { value = aws_db.admin.password sensitive = true }

Solution

1. Step 1: Identify which outputs should be sensitive

   The admin password must be hidden, so sensitive = true is needed there.

2. Step 2: Confirm app URL visibility

   The app URL should be visible, so no sensitive flag on that output.

3. Final Answer:

   output "app_url" { value = aws_lb.web.dns_name } output "admin_password" { value = aws_db.admin.password sensitive = true } -> Option B

4. Quick Check:

   Hide secrets, show URLs = A [OK]

Hint: Set sensitive = true only on secret outputs [OK]

Common Mistakes:

• Marking non-secret outputs as sensitive
• Not marking secrets as sensitive
• Hiding all outputs unnecessarily