3.1. Resources

Preparation

Create a new directory for this exercise:

mkdir -p $LAB_ROOT/basics/resources
cd $LAB_ROOT/basics/resources

Step 3.1.1: Create main.tf

We will start with a simple example by creating a resource of type random_integer. This resources generates a random number in the configured range.

Create a new file named main.tf in your working directory and paste the following:

resource "random_integer" "number" {
  min = 1000
  max = 9999
}

Explanation

The resource block defines one (or multiple) infrastructure objects which are managed by Terraform.

For more information about Terraform resources, please see https://www.terraform.io/docs/language/resources/syntax.html

Step 3.1.2: Init Terraform

Download all required Terraform providers and initialize the local state:

terraform init

Output:

Initializing the backend...

Initializing provider plugins...
- Finding latest version of hashicorp/random...
- Installing hashicorp/random v3.5.1...
- Installed hashicorp/random v3.5.1 (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
so that Terraform can guarantee to make the same selections by default when
you run "terraform init" in the future.

Terraform has been successfully initialized!

Step 3.1.3: Plan execution

The planing will help Terraform to understand your configuration and verify the syntax. To create a provisioning plan, run:

terraform plan

This will show output similar to:

Terraform will perform the following actions:

  # random_integer.acr will be created
  + resource "random_integer" "number" {
      + id     = (known after apply)
      + min    = 1000
      + max    = 9999
      + result = (known after apply)
    }

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

Step 3.1.4: Apply configuration

After planing the infrastructure provisioning, we instruct Terraform to apply the configuration:

terraform apply

Terraform will print the execution plan again and ask for confirmation. Type yes to continue.

random_integer.number: Creating...
random_integer.number: Creation complete after 0s [id=9437]

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

Step 3.1.5: Inspect the local state

After creating the resources you might wonder, where Terraform stores the generated number? As we are not in the cloud yet, where is the state stored?

Run the following command:

ls -l

There is a file called terraform.tfstate which contains all information of your resources provisioned by Terraform. Your random number is stored in this file. Terraform requires a .tfstate file to store all your configurations. It is used to compare your desired state (in code) against the real world (fetched by APIs) and last execution (stored in the state) plus objects not available by API resource like random passwords, SSL certs (also stored in the state).

In a later chapter we will learn how store this file in the cloud and why it is best practice.

Step 3.1.6: Destruction

To remove or de-provision all resources, run the following command:

terraform destroy

Terraform will again ask for confirmation if you want destroy the content. Type yes to destroy all resources managed by this Terraform code base (aka. stack).