Terraform plan for preview - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the terraform plan command do?

It shows a preview of the changes Terraform will make to your infrastructure without applying them. It helps you understand what will be created, changed, or destroyed.

beginner

Why is it important to run terraform plan before terraform apply?

Running terraform plan helps catch mistakes early by showing what changes will happen. This prevents unexpected or harmful changes to your infrastructure.

beginner

What does it mean if terraform plan shows no changes?

It means your current infrastructure matches the configuration files exactly, so no updates, creations, or deletions are needed.

intermediate

How can you save the output of terraform plan for later use?

You can save the plan to a file using terraform plan -out=planfile. Later, you can apply this exact plan with terraform apply planfile.

beginner

What is the difference between terraform plan and terraform apply?

terraform plan previews changes without making them. terraform apply actually makes the changes to your infrastructure.

What does terraform plan primarily do?

A Initializes Terraform configuration

B Shows a preview of infrastructure changes

C Deletes all resources

D Applies changes to infrastructure

terraform plan previews changes without applying them.

How do you save a Terraform plan to a file?

A terraform plan -out=planfile

B terraform plan -save=planfile

C terraform save planfile

D terraform apply -plan=planfile

Use terraform plan -out=planfile to save the plan.

If terraform plan shows no changes, what does it mean?

A Terraform will destroy all resources

B Terraform configuration has errors

C Your infrastructure matches the configuration

D Terraform will create new resources

No changes means infrastructure matches the config.

Which command actually makes changes to your infrastructure?

A terraform apply

B terraform init

C terraform plan

D terraform validate

terraform apply applies the planned changes.

Why should you run terraform plan before terraform apply?

A To backup your infrastructure

B To delete resources

C To initialize Terraform

D To preview changes and avoid mistakes

Planning helps catch mistakes before applying changes.

Explain the purpose and benefits of using terraform plan in your workflow.

Think about how seeing changes before applying helps you.

Describe the difference between terraform plan and terraform apply.

One shows what will happen, the other makes it happen.

Practice

1. What is the main purpose of the terraform plan command?

easy

A. To destroy all existing infrastructure

B. To apply changes directly to cloud resources

C. To initialize the Terraform working directory

D. To preview changes Terraform will make without applying them

Solution

1. Step 1: Understand the role of terraform plan

   This command shows what changes Terraform will make but does not apply them.

2. Step 2: Compare with other commands

   terraform apply applies changes, terraform destroy removes resources, and terraform init initializes the directory.

3. Final Answer:

   To preview changes Terraform will make without applying them -> Option D

4. Quick Check:

   Preview changes = terraform plan [OK]

Hint: Plan previews changes, apply makes changes [OK]

Common Mistakes:

• Confusing plan with apply
• Thinking plan modifies resources
• Mixing plan with init or destroy

2. Which of the following is the correct syntax to run a Terraform plan with a specific variable file named vars.tfvars?

easy

A. terraform plan --vars-file=vars.tfvars

B. terraform plan --varfile vars.tfvars

C. terraform plan -var-file=vars.tfvars

D. terraform plan -varfile=vars.tfvars

Solution

1. Step 1: Recall correct flag for variable files

   The correct flag is -var-file with a hyphen between var and file.

2. Step 2: Check syntax correctness

   terraform plan -var-file=vars.tfvars uses -var-file=vars.tfvars, which is the official syntax. Other options use incorrect flags.

3. Final Answer:

   terraform plan -var-file=vars.tfvars -> Option C

4. Quick Check:

   Use -var-file=filename for variable files [OK]

Hint: Use -var-file=filename to specify variable files [OK]

Common Mistakes:

• Using --varfile instead of -var-file
• Mixing underscores or missing hyphens
• Using --vars-file which is invalid

3. Given this Terraform plan output snippet:

  # aws_instance.example will be created
  + resource "aws_instance" "example" {
      + ami           = "ami-123456"
      + instance_type = "t2.micro"
    }

What does the plus sign (+) before the resource indicate?

medium

A. The resource will be created

B. The resource will be destroyed

C. The resource will be updated in place

D. The resource is unchanged

Solution

1. Step 1: Understand Terraform plan symbols

   The plus sign (+) means Terraform plans to add or create the resource.

2. Step 2: Differentiate from other symbols

   Minus (-) means destroy, ~ means update, no symbol means unchanged.

3. Final Answer:

   The resource will be created -> Option A

4. Quick Check:

   Plus sign (+) = create resource [OK]

Hint: Plus (+) means create, minus (-) means destroy [OK]

Common Mistakes:

• Confusing + with update or destroy
• Ignoring symbols and guessing
• Assuming no symbol means create

4. You run terraform plan but get this error:

Error: No configuration files found!

What is the most likely cause?

medium

A. You ran the command outside the Terraform configuration directory

B. You forgot to run terraform init first

C. Your Terraform version is outdated

D. Your cloud provider credentials are missing

Solution

1. Step 1: Analyze the error message

   The error says no configuration files found, meaning Terraform can't find .tf files.

2. Step 2: Identify common causes

   This usually happens if you run the command outside the folder containing Terraform files.

3. Final Answer:

   You ran the command outside the Terraform configuration directory -> Option A

4. Quick Check:

   No config files = wrong directory [OK]

Hint: Run plan inside folder with .tf files [OK]

Common Mistakes:

• Assuming init fixes missing files
• Blaming credentials for config file errors
• Ignoring current working directory

5. You want to preview changes only for a specific resource named aws_s3_bucket.mybucket without affecting others. Which command achieves this?

hard

A. terraform plan -only=aws_s3_bucket.mybucket

B. terraform plan -target=aws_s3_bucket.mybucket

C. terraform plan --filter=aws_s3_bucket.mybucket

D. terraform plan -resource=aws_s3_bucket.mybucket

Solution

1. Step 1: Recall how to target specific resources in plan

   The -target flag limits the plan to specified resources.

2. Step 2: Verify correct flag usage

   terraform plan -target=aws_s3_bucket.mybucket uses -target=aws_s3_bucket.mybucket, which is the correct syntax. Other options are invalid flags.

3. Final Answer:

   terraform plan -target=aws_s3_bucket.mybucket -> Option B

4. Quick Check:

   Use -target to preview specific resources [OK]

Hint: Use -target=resource_name to limit plan scope [OK]

Common Mistakes:

• Using non-existent flags like -only or --filter
• Forgetting to specify resource type and name
• Assuming plan always shows all resources