Demo Terraform CLI

This tutorial demonstrates common Terraform CLI workflows by creating a minimal Terraform configuration that uses the built-in random provider. You will:

author a simple configuration that generates a short “pet” name,
initialize the working directory,
validate and plan changes,
apply and inspect state,
change the configuration to trigger resource replacement, and
destroy the resources.

Relevant references:

Terraform CLI reference: https://developer.hashicorp.com/terraform/cli
random provider docs: https://registry.terraform.io/providers/hashicorp/random/latest/docs

Prerequisites

Terraform installed and on your PATH. Confirm with terraform version.
An empty working directory for this demo.

1 — Create the configuration

Create a file named main.tf with the following configuration. This uses the random_pet resource to create a short, human-readable name.

provider "random" {}

resource "random_pet" "name" {
  length = 2
}

output "random_pet_name" {
  value = random_pet.name.id
}

Save the file and continue to the CLI steps below.

2 — Verify Terraform installation

Check that Terraform is installed and view the version:

terraform version

Example output:

Terraform v1.10.5
on darwin_arm64

3 — Format the configuration (optional)

Keep your files consistent with:

terraform fmt

4 — Initialize the working directory

Initialize the directory to download provider plugins and create the .terraform directory and lockfile:

terraform init

Example (truncated):

Initializing provider plugins...
- Finding latest version of hashicorp/random...
- Installing hashicorp/random v3.6.3...
- Installed hashicorp/random v3.6.3 (signed by HashiCorp)

Terraform has created a lock file .terraform.lock.hcl to record the provider
selections it made above. Include this file in your version control repository.

Terraform has been successfully initialized!

You may now begin working with Terraform. Try running "terraform plan" to see
any changes that are required for your infrastructure.

5 — Validate configuration

Validate that the configuration syntax and references are correct:

terraform validate

Success message:

Success! The configuration is valid.

Example validation error (if an output references a nonexistent resource):

Error: Reference to undeclared resource

  on main.tf line 8, in output "random_pet_name":
   8:     value = random_pet.id

A managed resource "random_pet" "id" has not been declared in the root module.

6 — Generate and inspect a plan

Preview what Terraform will do without making changes:

terraform plan

Example plan (truncated):

Terraform used the selected provider(s) to generate the following execution plan.
Resource actions are indicated with the following symbols:
  + create

Terraform will perform the following actions:

  # random_pet.name will be created
  + resource "random_pet" "name" {
      + id        = (known after apply)
      + length    = 2
      + separator = "-"
    }

Plan: 1 to add, 0 to change, 0 to destroy.

Changes to Outputs:
  + random_pet_name = (known after apply)

Note: You didn't use the -out option to save this plan, so Terraform can't guarantee to take exactly these actions if you run "terraform apply" now.

Save a plan to a file (optional)

To ensure you apply exactly the same plan later, save it:

terraform plan -out=bryan

Example output:

Saved the plan to: bryan

To perform exactly these actions, run the following command to apply:
  terraform apply "bryan"

7 — Apply the plan (create resources)

Apply changes. By default Terraform will prompt for confirmation:

terraform apply

Type yes at the prompt to proceed. Example interaction:

Do you want to perform these actions?
  Terraform will perform the actions described above.
  Only 'yes' will be accepted to approve.

Enter a value: yes

random_pet.name: Creating...
random_pet.name: Creation complete after 0s [id=better-caribou]

Apply complete! Resources: 1 added, 0 changed, 0 destroyed.

Outputs:

random_pet_name = "better-caribou"

To skip interactive confirmation (use only in automation):

terraform apply -auto-approve

Using -auto-approve (for apply or destroy) skips interactive confirmation. Use it only in automated contexts where you are sure about the changes.

8 — Change the resource (replacement behavior)

Edit main.tf to change the random_pet length from 2 to 3:

provider "random" {}

resource "random_pet" "name" {
  length = 3
}

output "random_pet_name" {
  value = random_pet.name.id
}

Run a plan to see what will happen:

terraform plan

Because increasing length forces replacement for random_pet in this provider, the plan will show a destroy and create action:

# random_pet.name must be replaced
-/+ resource "random_pet" "name" {
  ~ id     = "better-caribou" -> (known after apply)
  ~ length = 2 -> 3 # forces replacement
  # (1 unchanged attribute hidden)
}

Plan: 1 to add, 0 to change, 1 to destroy.

Changes to Outputs:
~ random_pet_name = "better-caribou" -> (known after apply)

Apply the change (example using auto-approve):

terraform apply -auto-approve

Example output:

random_pet.name: Destroying... [id=better-caribou]
random_pet.name: Destruction complete after 0s
random_pet.name: Creating...
random_pet.name: Creation complete after 0s [id=painfully-rich-mongrel]

Apply complete! Resources: 1 added, 0 changed, 1 destroyed.

Outputs:

random_pet_name = "painfully-rich-mongrel"

9 — Inspect the Terraform state

Terraform records metadata about managed resources in the state file (e.g., terraform.tfstate). You can examine the state file directly or use state subcommands. JSON excerpt of the state outputs (example):

{
  "version": 4,
  "terraform_version": "1.10.5",
  "serial": 5,
  "lineage": "8072588f-d48c-d854-1b42-13df2b07cae7",
  "outputs": {
    "random_pet_name": {
      "value": "painfully-rich-mongrel",
      "type": "string"
    }
  }
}

List resources tracked in state:

terraform state list

10 — Destroy resources

When finished, destroy the managed resources:

terraform destroy

You will be prompted to confirm by typing yes:

Terraform will destroy all your managed infrastructure, as shown above.
There is no undo. Only 'yes' will be accepted to confirm.

Enter a value: yes

random_pet.name: Destroying... [id=painfully-rich-mongrel]
random_pet.name: Destruction complete after 0s

Destroy complete! Resources: 1 destroyed.

To skip confirmation (use with caution):

terraform destroy -auto-approve

11 — Multiple resources and unique labels

If you add multiple resources of the same type, each resource block must have a unique label (allowed characters: letters, digits, and underscores). Example adding another random_pet resource:

resource "random_pet" "name" {
  length = 3
}

resource "random_pet" "bryans_pet" {
  length = 3
}

output "random_pet_name" {
  value = random_pet.name.id
}

Apply and then list state:

terraform apply
terraform state list

Example terraform state list output:

random_pet.bryans_pet
random_pet.name

When finished, use terraform destroy -auto-approve to remove everything.

Quick reference — common Terraform CLI commands

Command	Purpose	Notes / Example
`terraform version`	Show installed Terraform version
`terraform fmt`	Format configuration files	Runs on current directory
`terraform init`	Initialize working directory and download providers	Creates `.terraform` and `.terraform.lock.hcl`
`terraform validate`	Validate configuration syntax and references	Detects missing resources or incorrect references
`terraform plan`	Show proposed changes	Use `-out=<file>` to save a plan
`terraform plan -out=<file>`	Save a generated plan to a file	Example: `terraform plan -out=bryan`
`terraform apply`	Apply changes (prompts for approval)	Use `-auto-approve` for non-interactive apply
`terraform state list`	List resources in state	Useful to inspect tracked resources
`terraform destroy`	Destroy managed resources	Use `-auto-approve` to skip confirmation

Links and references

Terraform CLI docs: https://developer.hashicorp.com/terraform/cli
random provider: https://registry.terraform.io/providers/hashicorp/random/latest/docs
Terraform docs (general): https://developer.hashicorp.com/terraform/docs

This concludes the Terraform CLI demonstration. Continue experimenting with different providers and resource types to learn how plan/apply/destroy behave with real infrastructure.

Course Introduction

Preparing Your Environment

Terraform Foundations

The Core Terraform Workflow

Terraform CLI

Terraform File Structure and Organization

Terraform Configuration - Fundamentals

Understading and Managing Terraform State

Marking Code Reusable

Refactoring Terraform State

Terraform Modules

Managing Resource Behavior and Dependencies

Securing Terraform Configurations

Terraform Troubleshooting

HCP Terraform

Demo Terraform CLI

Prerequisites

1 — Create the configuration

2 — Verify Terraform installation

3 — Format the configuration (optional)

4 — Initialize the working directory

5 — Validate configuration

6 — Generate and inspect a plan

Save a plan to a file (optional)

7 — Apply the plan (create resources)

8 — Change the resource (replacement behavior)

9 — Inspect the Terraform state

10 — Destroy resources

11 — Multiple resources and unique labels

Quick reference — common Terraform CLI commands

Links and references

Watch Video

​Prerequisites

​1 — Create the configuration

​2 — Verify Terraform installation

​3 — Format the configuration (optional)

​4 — Initialize the working directory

​5 — Validate configuration

​6 — Generate and inspect a plan

​Save a plan to a file (optional)

​7 — Apply the plan (create resources)

​8 — Change the resource (replacement behavior)

​9 — Inspect the Terraform state

​10 — Destroy resources

​11 — Multiple resources and unique labels

​Quick reference — common Terraform CLI commands

​Links and references

Watch Video

Prerequisites

1 — Create the configuration

2 — Verify Terraform installation

3 — Format the configuration (optional)

4 — Initialize the working directory

5 — Validate configuration

6 — Generate and inspect a plan

Save a plan to a file (optional)

7 — Apply the plan (create resources)

8 — Change the resource (replacement behavior)

9 — Inspect the Terraform state

10 — Destroy resources

11 — Multiple resources and unique labels

Quick reference — common Terraform CLI commands

Links and references