Terraform CLI overview - Step-by-Step Execution

Process Flow - Terraform CLI overview

Start: User writes Terraform config

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Run 'terraform init'

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Terraform downloads providers

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Run 'terraform plan'

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Terraform shows planned changes

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Run 'terraform apply'

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Terraform creates/updates infrastructure

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Run 'terraform destroy'

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Terraform deletes infrastructure

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End

This flow shows how a user writes config, initializes Terraform, plans changes, applies them, and optionally destroys infrastructure.

Execution Sample

Terraform

terraform init
terraform plan
terraform apply
terraform destroy

These commands initialize Terraform, show planned changes, apply them, and destroy resources.

Process Table

Step	Command	Action	Result
1	terraform init	Initialize working directory and download providers	Providers downloaded, backend configured
2	terraform plan	Create execution plan	Shows what will be created/changed/destroyed
3	terraform apply	Apply changes to infrastructure	Resources created/updated as planned
4	terraform destroy	Destroy all managed infrastructure	Resources deleted
5	-	End of workflow	No further actions

💡 Workflow ends after destroy or when no further changes are needed

Status Tracker

Variable	Start	After init	After plan	After apply	After destroy
Working Directory	Empty	Initialized with .terraform folder	Plan generated	Infrastructure state updated	Infrastructure state cleared
Providers	Not downloaded	Downloaded	Used for plan	Used for apply	Used for destroy
State File	None	None	None	Created/Updated	Cleared

Key Moments - 3 Insights

Why do we run 'terraform init' before other commands?

'terraform init' sets up the working directory and downloads necessary providers. Without it, 'plan' or 'apply' will fail. See execution_table step 1.

What does 'terraform plan' do if no changes are detected?

'terraform plan' will show that no changes are needed and no resources will be created or modified. This is shown in execution_table step 2.

Does 'terraform apply' always create new resources?

'terraform apply' only creates or updates resources if the plan shows changes. Otherwise, it does nothing. See execution_table step 3.

Visual Quiz - 3 Questions

Look at the execution_table, what is the result of running 'terraform init'?

A Resources created

B Execution plan created

C Providers downloaded, backend configured

D Resources destroyed

💡 Hint

Check execution_table row 1 under Result column

At which step does Terraform show what changes it will make?

A terraform plan

B terraform init

C terraform apply

D terraform destroy

💡 Hint

See execution_table step 2 Action and Result

If you want to remove all infrastructure, which command do you run?

A terraform plan

B terraform destroy

C terraform init

D terraform apply

💡 Hint

Look at execution_table step 4 Command and Result

Concept Snapshot

Terraform CLI commands:
- terraform init: sets up directory and downloads providers
- terraform plan: shows what changes will happen
- terraform apply: makes changes to infrastructure
- terraform destroy: deletes all managed resources
Always run init first before plan or apply.

Full Transcript

Terraform CLI is a set of commands to manage infrastructure. First, you write your configuration files. Then you run 'terraform init' to prepare your working directory and download necessary providers. Next, 'terraform plan' shows you what changes Terraform will make. If you agree, 'terraform apply' makes those changes to your cloud resources. When you want to remove everything, 'terraform destroy' deletes all managed infrastructure. This workflow helps you safely create, update, and delete cloud resources using simple commands.

Practice

1. What is the primary purpose of the terraform init command?

easy

A. To show the planned changes without applying them

B. To apply changes to cloud infrastructure

C. To destroy all managed resources

D. To initialize a working directory and download required provider plugins

Solution

1. Step 1: Understand the role of terraform init

   This command sets up the working directory by downloading necessary provider plugins and preparing the environment.

2. Step 2: Differentiate from other commands

   Commands like apply and destroy perform changes, while init only prepares the setup.

3. Final Answer:

   To initialize a working directory and download required provider plugins -> Option D

4. Quick Check:

   terraform init prepares environment [OK]

Hint: Init sets up your folder and downloads plugins [OK]

Common Mistakes:

• Confusing init with apply
• Thinking init changes infrastructure
• Mixing init with destroy

2. Which of the following is the correct syntax to preview changes without applying them?

easy

A. terraform plan

B. terraform apply --preview

C. terraform preview

D. terraform show

Solution

1. Step 1: Identify the command to preview changes

   terraform plan shows what changes will happen without applying them.

2. Step 2: Check other options for correctness

   apply --preview and preview are not valid commands; show displays current state, not planned changes.

3. Final Answer:

   terraform plan -> Option A

4. Quick Check:

   Preview changes = terraform plan [OK]

Hint: Plan shows changes without applying [OK]

Common Mistakes:

• Using apply --preview which is invalid
• Confusing show with plan
• Assuming preview is a Terraform command

3. Given the following sequence of commands:

terraform init
tf plan
terraform apply

What will happen when you run these commands?

medium

A. Only initialize the directory and apply changes, skipping the plan

B. Initialize the directory, show planned changes, then apply those changes

C. Initialize the directory, apply changes immediately, then show the plan

D. Show planned changes without initializing or applying

Solution

1. Step 1: Understand each command's role

   terraform init sets up the environment, terraform plan shows what will change, and terraform apply makes those changes.

2. Step 2: Analyze the sequence

   The commands run in order: initialize, plan, then apply, which is the recommended workflow.

3. Final Answer:

   Initialize the directory, show planned changes, then apply those changes -> Option B

4. Quick Check:

   Init -> Plan -> Apply = safe workflow [OK]

Hint: Init, then plan, then apply changes [OK]

Common Mistakes:

• Running apply before plan
• Skipping init before plan
• Confusing plan and apply order

4. You run terraform apply but get an error saying the backend is not configured. What is the most likely cause?

medium

A. You need to run terraform destroy first

B. You used the wrong syntax for apply

C. You forgot to run terraform init first

D. Your cloud provider credentials are missing

Solution

1. Step 1: Understand backend configuration role

   The backend stores state remotely and must be set up before applying changes.

2. Step 2: Identify how backend is configured

   terraform init configures the backend; skipping it causes errors.

3. Final Answer:

   You forgot to run terraform init first -> Option C

4. Quick Check:

   Init configures backend before apply [OK]

Hint: Always run init before apply to configure backend [OK]

Common Mistakes:

• Skipping init and running apply directly
• Assuming credentials cause backend error
• Thinking destroy fixes backend issues

5. You want to safely remove all cloud resources managed by Terraform. Which command sequence ensures this with minimal risk?

hard

A. terraform destroy after terraform plan to review changes

B. terraform apply followed by terraform destroy

C. terraform init then terraform apply

D. terraform plan then terraform init

Solution

1. Step 1: Understand the purpose of terraform destroy

   This command deletes all resources managed by Terraform.

2. Step 2: Use terraform plan before destroy

   Planning shows what will be destroyed, helping avoid mistakes.

3. Step 3: Confirm the sequence

   Running terraform plan first, then terraform destroy is the safest approach.

4. Final Answer:

   terraform destroy after terraform plan to review changes -> Option A

5. Quick Check:

   Plan before destroy to avoid surprises [OK]

Hint: Plan first, then destroy to confirm changes [OK]

Common Mistakes:

• Destroying without planning first
• Applying changes before destroying
• Running init after plan