How to Import an Azure Subnet NSG Association into Terraform

Import Azure Subnet NSG Association with Terraback (recommended)

Terraback reverse-engineers your live infrastructure: it reads the Azure Networking resource with read-only credentials, generates the HCL, and produces the exact import block. Two commands take you from a live Azure Subnet NSG Association 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_subnet_network_security_group_association.internal
  id = "/subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/prod-rg/providers/Microsoft.Network/virtualNetworks/prod-vnet/subnets/internal"
}

Example azurerm_subnet_network_security_group_association configuration

Here is a realistic Azure Subnet NSG Association block. Terraback generates a fuller version from your actual resource attributes; this is a minimal, valid starting point.

resource "azurerm_subnet_network_security_group_association" "internal" {
  subnet_id                 = azurerm_subnet.internal.id
  network_security_group_id = azurerm_network_security_group.internal.id
}

Gotchas when importing a Azure Subnet NSG Association

• The import ID is the SUBNET resource ID, not an ID of the association itself, and not the NSG ID.
• This is a glue resource: the subnet and the NSG both exist and import on their own as azurerm_subnet and azurerm_network_security_group.
• Do not also set network_security_group_id inline on the azurerm_subnet; managing the association both inline and via this resource causes drift.
• Each subnet can be associated with at most one NSG, so there is one association per subnet.

Doing it manually with terraform import

The native approach is to write the azurerm_subnet_network_security_group_association block by hand, then run terraform import azurerm_subnet_network_security_group_association.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