Providers & Resources

Let's think about this for a second

You configure a provider block like `provider "aws" { region = "us-east-1" }` — each provider has its own authentication method (for AWS: access key/secret key, environment variables, or an IAM role). Resource type names (`aws_instance`, `aws_s3_bucket`, `azurerm_virtual_machine`) include the provider name as a prefix — you can look up every argument for a given resource type in the provider's documentation on the Terraform Registry. You should constrain the provider version in the `required_providers` block, to guard against a version update suddenly breaking your config.

Let's connect this to a real scenario

If you open the Terraform Registry (registry.terraform.io) and look up the `aws_instance` resource's documentation, you can read every argument (ami, instance_type, tags) — whenever you want to use a new resource, it's worth checking the Registry for its argument list. Writing a provider version as `~> 5.0` means 'any 5.x minor version is fine.'

provider block = sets up provider config (region, credentials)
resource type name = includes a provider prefix (aws_instance, azurerm_...)
required_providers version constraints = guard against unexpected breaking updates

Let's look at an example

hcl

terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 5.0"
    }
  }
}

provider "aws" {
  region = "us-east-1"
}

resource "aws_instance" "web" {
  ami           = "ami-0abcdef1234567890"
  instance_type = "t3.micro"

  tags = {
    Name = "tutorial-web-server"
  }
}

You should see

$ terraform plan
  + resource "aws_instance" "web" {
      + ami           = "ami-0abcdef1234567890"
      + instance_type = "t3.micro"
      ...
    }
Plan: 1 to add, 0 to change, 0 to destroy.

5-minute try-it

Open the Terraform Registry website and look up the documentation for `aws_s3_bucket` (or a provider of your choice) — note down which arguments are required.

A quick word of caution

A resource type's arguments (required vs optional) can change between provider versions — always check the Registry documentation for the exact provider version you're using.