=====Terraform up and running=====
language: .hcl Hashicorp Configuration Language
syntax:
  <block type> "<block label>" "<block label>"{
  #body block
  <identifier> = <expression>
  }
ex:
  resource "google_compute_network" "default" {
  #comment
  name                    = mynetwork
  auto_create_subnetworks = false
  }

phases:
  * author
  * init
  * plan
  * apply

directories:
<code>
  -- main.tf                              ]root module
    -- servers/                           _
      -- main.tf                           | 
      -- providers.tf                      | child Module
      -- variables.tf                      |
      -- outputs.tf                        |
                                      

</code>



terraform plug-in calls providers

reusable terraform configurations called modules

terraform configuration languages il declarative
it consists in 5 step:
 - scope: identify your project
 - author: write your code
 - initialize: install needed plugins, providers
 - plan: preview changes
 - apply: make changes

=====resources=====
inside main.tf
  resource "google_storage_bucket" "example_bucket"{
      name     = "unique-bucket-name"
      location = "US"
  }
  
  resource "google_compute_instance" "examplre_compute" {
      name                    = "test"
      machine-type            = "e2-medium"
      zone                    = "us-central1-a"
      boot_disk {
          initialize_params {
              image = "debian-cloud/debian-9"
          }
      }
   } 
   
=====providers=====

you can find the list of providers here:
[[https://registry.terraform.io/providers/hashicorp/google/latest|providers ]]
for google:
[[https://registry.terraform.io/providers/hashicorp/google/latest|google]]

if not defined assueed as default.
inside providers.tf

  terraform {
      required_providers {
          google = {
              source  = "hashicorp/google"
              version = "4.23.0"
      }
  } 
  
  provider "google" {
      project = "project_id"
      region  = "us-central1-"
  }

=====variables.tf=====
variables.ts

=====outputs.tf=====
holds output values from your resources

=====terraform.tfstate======
terraform saves the state of resources it manages in a state file, stored locally or remotely
=====trying with docker=====

copy and paste in main.tf file the following code:
<code>
terraform {
  required_providers {
    docker = {
      source  = "kreuzwerker/docker"
     # version = "~> 2.15.0"
      version = "3.0.2"
    }
  }
}

provider "docker" {}

resource "docker_image" "nginx" {
  name         = "nginx:latest"
  keep_locally = false
}

resource "docker_container" "nginx" {
  #image = docker_image.nginx.latest
  image = docker_image.nginx.image_id #latest doesn't exist
  name  = "tutorial"
  ports {
    internal = 80
    external = 8000
  }
}
</code>  

after this you can issue

  terraform init

in the event we need to change the provider, it is mandatory to reissue 
terraform init --upgrade

then apply the configuration with

  terraform apply

then remove it with 

  terraform destroy

after this pay particular attention to the state file where terraform save the status of the application