Terraform: Reference Current Infra

Description:

Many times we will need to reference current resources and then pass other information to build on them. For example, adding a Virtual Machine to an already existing Resource Group. I’m not sure how to modify these resources just yet, that will have to be a different post.

To Resolve:

1. To get the resource ID of the current subscription:

   data "azurerm_subscription" "current" {}
   
   output "sub_name" {
      value = data.azurerm_subscription.current.id
   }
   
   output "tenant_name" {
      value = data.azurerm_subscription.current.tenant_id
   }
   

   • Output:

   sub_name    = "/subscriptions/subscription-id-guid"
   tenant_name = "tenant-id-guid"
   

2. You can do this for any existing resource. For example:

   data "azurerm_virtual_network" "vnet" {
      name                = var.vnet_name
      resource_group_name = var.rg
   }
   
   data "azurerm_subnet" "my_subnet" {
      resource_group_name  = var.rg
      virtual_network_name = data.azurerm_virtual_network.vnet.name
      name                 = var.subnet_name
   }
   

   • You can reference them by syntax: data.$ARM_Resource_Name.$Alias.output where ARM_Resource_Name matches the resource in Azure Docs and $alias is whatever label you give the resource.

3. You can check outputs by going to their AzureRM (ARM) documents at AzureRM Docs

   • For example, I see Virtual Network has many attributes exported such as id, name, resource_group_name, and more.

   • This means that later in my code I can reference like: data.azurerm_virtual_network.vnet.resource_group_name for example or data.azurerm_virtual_network.vnet.name