Plan and apply separation in pipelines in Terraform - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of separating 'plan' and 'apply' stages in Terraform pipelines?

Separating 'plan' and 'apply' stages helps to review and approve infrastructure changes before they are made, reducing errors and improving control.

beginner

In Terraform pipelines, what does the 'terraform plan' command do?

It creates an execution plan showing what changes Terraform will make to reach the desired state without applying them.

intermediate

Why is it important to store the Terraform plan output and use it in the apply stage?

Storing the plan output ensures that the exact reviewed plan is applied, preventing unexpected changes during apply.

intermediate

How can manual approval be integrated between plan and apply stages in a pipeline?

By adding a manual approval step after the plan stage, teams can review the plan output and confirm before applying changes.

beginner

What is a common tool or service used to automate Terraform pipelines with plan and apply separation?

CI/CD tools like GitHub Actions, GitLab CI, or Jenkins are commonly used to automate Terraform pipelines with separate plan and apply stages.

What does the 'terraform apply' command do?

A Shows the planned changes without applying them

B Validates the Terraform configuration syntax only

C Applies the changes to reach the desired infrastructure state

D Deletes all infrastructure resources

The 'terraform apply' command executes the planned changes to create, update, or delete infrastructure resources.

Why should the plan output be saved and reused in the apply stage?

A To speed up the apply process

B To automatically approve changes

C To avoid running terraform init again

D To ensure the exact reviewed plan is applied

Saving the plan output ensures that the apply stage uses the exact plan reviewed, preventing unexpected changes.

What is a benefit of adding a manual approval step between plan and apply?

A It allows review and prevents accidental changes

B It speeds up deployment

C It automatically fixes errors

D It removes the need for version control

Manual approval lets team members review planned changes before applying, reducing risk of mistakes.

Which command generates a Terraform execution plan?

A terraform plan

B terraform apply

C terraform init

D terraform validate

'terraform plan' creates a preview of changes without applying them.

Which tool can be used to automate Terraform pipelines with plan and apply separation?

A Microsoft Word

B GitHub Actions

C Adobe Photoshop

D Slack

GitHub Actions is a CI/CD tool that can automate Terraform pipelines including separate plan and apply stages.

Explain why separating the 'plan' and 'apply' stages in Terraform pipelines is a best practice.

Think about how reviewing before doing helps avoid mistakes.

Describe how you would implement a pipeline that separates Terraform plan and apply stages with manual approval.

Consider the flow from planning to approval to applying.

Practice

1. What is the main benefit of separating terraform plan and terraform apply in pipelines?

easy

A. It speeds up the deployment by combining steps

B. It skips the need for state files

C. It automatically fixes errors during apply

D. It allows you to review changes before applying them

Solution

1. Step 1: Understand the purpose of terraform plan

   This command shows what changes Terraform will make without applying them.

2. Step 2: Understand the purpose of terraform apply

   This command applies the changes to the infrastructure based on the plan.

3. Final Answer:

   It allows you to review changes before applying them -> Option D

4. Quick Check:

   Plan shows changes first = B [OK]

Hint: Plan shows changes, apply makes them live [OK]

Common Mistakes:

• Thinking plan applies changes
• Believing apply skips state files
• Assuming steps run faster combined

2. Which command correctly saves a Terraform plan to a file named myplan.tfplan?

easy

A. terraform apply -out=myplan.tfplan

B. terraform save myplan.tfplan

C. terraform plan -out=myplan.tfplan

D. terraform plan save myplan.tfplan

Solution

1. Step 1: Identify the correct syntax for saving a plan

   The correct command uses terraform plan -out=filename to save the plan.

2. Step 2: Check each option

   terraform plan -out=myplan.tfplan matches the correct syntax exactly.

3. Final Answer:

   terraform plan -out=myplan.tfplan -> Option C

4. Quick Check:

   Plan with -out saves file = C [OK]

Hint: Use 'plan -out=' to save plans, not apply [OK]

Common Mistakes:

• Using apply instead of plan to save
• Using incorrect command like 'save'
• Missing the '-out=' flag

3. Given these commands run in order:
terraform plan -out=planfile
terraform apply planfile
What happens when you run terraform apply planfile?

medium

A. Terraform applies exactly the changes saved in planfile

B. Terraform ignores planfile and creates a new plan

C. Terraform applies changes but may differ from planfile

D. Terraform throws an error because planfile is not a valid command

Solution

1. Step 1: Understand the role of the saved plan file

   The plan file contains the exact changes Terraform will apply.

2. Step 2: Understand how terraform apply planfile works

   This command applies the saved plan exactly, without recalculating changes.

3. Final Answer:

   Terraform applies exactly the changes saved in planfile -> Option A

4. Quick Check:

   Apply saved plan = exact changes [OK]

Hint: Apply with plan file applies exact saved changes [OK]

Common Mistakes:

• Thinking apply recalculates plan
• Assuming apply ignores plan file
• Believing apply with plan file causes errors

4. You run terraform apply myplan.tfplan but get an error saying the plan file is invalid. What is the most likely cause?

medium

A. You forgot to run terraform init before apply

B. The plan file was created with a different Terraform version

C. You used terraform plan without -out flag

D. The plan file is empty because no changes were detected

Solution

1. Step 1: Identify compatibility issues with plan files

   Plan files are version-specific and may be invalid if Terraform versions differ.

2. Step 2: Check other options

   Running init is required but usually causes different errors; missing -out means no plan file saved; empty plan files do not cause invalid file errors.

3. Final Answer:

   The plan file was created with a different Terraform version -> Option B

4. Quick Check:

   Version mismatch causes invalid plan file error [OK]

Hint: Check Terraform versions match when using saved plans [OK]

Common Mistakes:

• Assuming missing init causes invalid plan file error
• Thinking empty plan files cause invalid file errors
• Confusing missing -out with invalid plan file

5. You want to implement a pipeline that separates planning and applying Terraform changes. Which sequence of commands ensures you can review the plan before applying exactly those changes?

hard

A. terraform plan -out=planfile && terraform apply planfile

B. terraform apply && terraform plan -out=planfile

C. terraform plan && terraform apply

D. terraform apply -out=planfile && terraform apply planfile

Solution

1. Step 1: Identify correct order for plan and apply separation

   First, run terraform plan -out=planfile to save the plan and review it.

2. Step 2: Apply the saved plan exactly

   Then, run terraform apply planfile to apply the reviewed changes exactly.

3. Final Answer:

   terraform plan -out=planfile && terraform apply planfile -> Option A

4. Quick Check:

   Plan with -out then apply saved plan = A [OK]

Hint: Plan with -out then apply saved plan file [OK]

Common Mistakes:

• Applying before planning
• Not saving plan with -out
• Using apply -out which is invalid