How to Import an Azure Windows VM Scale Set into Terraform

Import Azure Windows VM Scale Set with Terraback (recommended)

Terraback reverse-engineers your live infrastructure: it reads the Azure Compute resource with read-only credentials, generates the HCL, and produces the exact import block. Two commands take you from a live Azure Windows VM Scale Set to managed Terraform.

terraback scan all azure --subscription-id YOUR_ID

terraback azure import --method bulk

The Terraform import block

Terraback emits a Terraform 1.5+ import block like the one below. Because the block lives in your configuration, the import is reviewable in a pull request and repeatable across environments.

import {
  to = azurerm_windows_virtual_machine_scale_set.app
  id = "/subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/prod-rg/providers/Microsoft.Compute/virtualMachineScaleSets/app-vmss"
}

Example azurerm_windows_virtual_machine_scale_set configuration

Here is a realistic Azure Windows VM Scale Set block. Terraback generates a fuller version from your actual resource attributes; this is a minimal, valid starting point.

resource "azurerm_windows_virtual_machine_scale_set" "app" {
  name                = "app-vmss"
  location            = "eastus"
  resource_group_name = "prod-rg"
  sku                 = "Standard_B2s"
  instances           = 3
  admin_username      = "azureuser"
  admin_password      = var.admin_password

  source_image_reference {
    publisher = "MicrosoftWindowsServer"
    offer     = "WindowsServer"
    sku       = "2022-datacenter-azure-edition"
    version   = "latest"
  }

  os_disk {
    caching              = "ReadWrite"
    storage_account_type = "Standard_LRS"
  }

  network_interface {
    name    = "primary"
    primary = true

    ip_configuration {
      name      = "internal"
      primary   = true
      subnet_id = azurerm_subnet.internal.id
    }
  }
}

Gotchas when importing a Azure Windows VM Scale Set

• Windows scale sets share the same ARM ID path (virtualMachineScaleSets) as Linux ones; the OS only determines the Terraform resource type.
• admin_password is required and is never returned by Azure, so it must be supplied in code (commonly via a variable).
• computer_name_prefix has a 9-character limit for Windows due to NetBIOS naming.
• Autoscale rules are a separate azurerm_monitor_autoscale_setting that references this scale set's ID.

Doing it manually with terraform import

The native approach is to write the azurerm_windows_virtual_machine_scale_set block by hand, then run terraform import azurerm_windows_virtual_machine_scale_set.example <import-id> for every resource, one at a time. That works for a handful of resources, but it does not scale: you author all the HCL yourself and repeat the command for each item. Terraback generates the HCL and the import blocks for your whole account in one pass.

Import other Azure resources