Terraform apply -replace flag - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the -replace flag do in terraform apply?

The -replace flag forces Terraform to destroy and recreate a specific resource during the apply process.

beginner

How do you specify a resource to replace using the -replace flag?

You specify the resource address, like -replace=aws_instance.example, to tell Terraform which resource to recreate.

intermediate

Why would you use the -replace flag instead of manually deleting a resource?

Using -replace lets Terraform handle the destruction and recreation safely, keeping the state consistent and avoiding manual errors.

intermediate

Can you replace multiple resources in one terraform apply command?

Yes, you can use multiple -replace flags to replace several resources at once.

advanced

What happens if you use -replace on a resource that does not exist in the state?

Terraform will show an error because it cannot replace a resource that is not tracked in the state.

What is the main purpose of the -replace flag in terraform apply?

A To force recreation of a resource

B To skip a resource during apply

C To update Terraform version

D To backup the state file

The -replace flag forces Terraform to destroy and recreate the specified resource.

How do you specify which resource to replace?

A By resource ID in the cloud provider

B By resource tag

C By resource name in the configuration file

D By resource address in Terraform state

You specify the resource address as tracked in the Terraform state, like aws_instance.example.

Can you replace multiple resources in one command?

A Yes, by using multiple <code>-replace</code> flags

B Yes, by listing resources separated by commas

C No, only one resource at a time

D No, you must run separate apply commands

Terraform allows multiple -replace flags in one apply command to replace several resources.

What happens if you try to replace a resource not in the state?

A Terraform creates a new resource

B Terraform shows an error

C Terraform ignores it

D Terraform deletes all resources

Terraform will show an error because it cannot replace a resource that is not tracked in the state.

Why is using -replace safer than manually deleting a resource?

A It updates the provider automatically

B It backs up the resource

C It keeps Terraform state consistent

D It speeds up apply time

Using -replace keeps the Terraform state consistent by managing destruction and recreation properly.

Explain how the -replace flag works in terraform apply and when you might use it.

Think about how Terraform manages resources and state.

Describe the steps Terraform takes when you run terraform apply -replace=resource.address.

Focus on the lifecycle of the resource during apply.

Practice

1. What does the -replace flag do when used with terraform apply?

easy

A. Only plans changes without applying them

B. Skips the creation of new resources

C. Forces Terraform to destroy and recreate a specific resource

D. Updates all resources without destroying any

Solution

1. Step 1: Understand the purpose of the -replace flag

   The -replace flag tells Terraform to destroy and recreate a specific resource during apply.

2. Step 2: Compare with other apply behaviors

   Normally, Terraform updates resources in place if possible, but -replace forces full replacement of the targeted resource.

3. Final Answer:

   Forces Terraform to destroy and recreate a specific resource -> Option C

4. Quick Check:

   -replace flag = force resource replacement [OK]

Hint: Remember: -replace means rebuild that resource only [OK]

Common Mistakes:

• Thinking -replace updates resources in place
• Confusing -replace with plan-only mode
• Assuming it affects all resources

2. Which of the following is the correct syntax to replace a resource named aws_instance.example using Terraform apply?

easy

A. terraform apply -replace=aws_instance.example

B. terraform apply --replace aws_instance.example

C. terraform apply -replace aws_instance.example

D. terraform apply -replace=aws_instance.example.id

Solution

1. Step 1: Recall the correct flag syntax

   The correct syntax uses an equals sign with the resource address: -replace=resource_address.

2. Step 2: Check the resource address format

   The resource address is aws_instance.example, so the correct command is terraform apply -replace=aws_instance.example.

3. Final Answer:

   terraform apply -replace=aws_instance.example -> Option A

4. Quick Check:

   Correct syntax uses '=' with resource address [OK]

Hint: Use '=' directly after -replace with resource name [OK]

Common Mistakes:

• Using space instead of '=' after -replace
• Adding extra flags like --replace
• Appending .id unnecessarily

3. Given this Terraform command:
terraform apply -replace=aws_s3_bucket.mybucket
What will happen to the resource aws_s3_bucket.mybucket during apply?

medium

A. It will be updated in place without destruction

B. It will be ignored and left unchanged

C. Terraform will only plan changes but not apply

D. It will be destroyed and recreated

Solution

1. Step 1: Understand the effect of -replace on a resource

   The -replace flag forces Terraform to destroy and recreate the specified resource during apply.

2. Step 2: Apply this to aws_s3_bucket.mybucket

   Since the command targets aws_s3_bucket.mybucket, Terraform will destroy and then recreate this bucket.

3. Final Answer:

   It will be destroyed and recreated -> Option D

4. Quick Check:

   -replace causes destroy and recreate [OK]

Hint: Replace means destroy then create that resource [OK]

Common Mistakes:

• Thinking it updates resource without destruction
• Assuming it skips the resource
• Confusing apply with plan

4. You run terraform apply -replace=aws_instance.web but get an error: Invalid resource address. What is the most likely cause?

medium

A. The resource name is misspelled or does not exist in the state

B. The -replace flag cannot be used with aws_instance resources

C. You forgot to run terraform init before apply

D. The command requires a space instead of '=' after -replace

Solution

1. Step 1: Analyze the error message

   An 'Invalid resource address' error means Terraform cannot find the resource in the state or the address is wrong.

2. Step 2: Check resource existence and spelling

   Most likely, the resource aws_instance.web is misspelled or not present in the current Terraform state.

3. Final Answer:

   The resource name is misspelled or does not exist in the state -> Option A

4. Quick Check:

   Invalid address = wrong or missing resource name [OK]

Hint: Check resource name spelling and state presence first [OK]

Common Mistakes:

• Assuming -replace flag is invalid for resource types
• Thinking terraform init fixes resource address errors
• Using space instead of '=' causes different errors

5. You want to replace two resources, aws_instance.web and aws_security_group.sg, in a single apply command. Which is the correct way to do this?

hard

A. terraform apply -replace=aws_instance.web,aws_security_group.sg

B. terraform apply -replace=aws_instance.web -replace=aws_security_group.sg

C. terraform apply -replace=aws_instance.web aws_security_group.sg

D. terraform apply -replace aws_instance.web -replace aws_security_group.sg

Solution

1. Step 1: Understand multiple -replace usage

   Terraform allows multiple -replace flags, each specifying one resource to replace.

2. Step 2: Evaluate each option

   terraform apply -replace=aws_instance.web -replace=aws_security_group.sg uses two separate -replace flags correctly. terraform apply -replace=aws_instance.web,aws_security_group.sg uses a comma which is invalid. Options C and D use incorrect syntax without '=' or with spaces.

3. Final Answer:

   terraform apply -replace=aws_instance.web -replace=aws_security_group.sg -> Option B

4. Quick Check:

   Use multiple -replace flags for multiple resources [OK]

Hint: Use one -replace= per resource to replace multiple [OK]

Common Mistakes:

• Trying to list multiple resources with commas
• Using spaces instead of '=' after -replace
• Combining resources in one -replace flag