How to Import an Google Compute Unmanaged Instance Group into Terraform

Import Google Compute Unmanaged Instance Group with Terraback (recommended)

Terraback reverse-engineers your live infrastructure: it reads the Compute Engine resource with read-only credentials, generates the HCL, and produces the exact import block. Two commands take you from a live Google Compute Unmanaged Instance Group to managed Terraform.

terraback scan all gcp --project my-gcp-project

terraback gcp 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 = google_compute_instance_group.web
  id = "projects/my-project/zones/us-central1-a/instanceGroups/web-ig"
}

Example google_compute_instance_group configuration

Here is a realistic Google Compute Unmanaged Instance Group block. Terraback generates a fuller version from your actual resource attributes; this is a minimal, valid starting point.

resource "google_compute_instance_group" "web" {
  name = "web-ig"
  zone = "us-central1-a"

  named_port {
    name = "http"
    port = 8080
  }
}

Gotchas when importing a Google Compute Unmanaged Instance Group

• google_compute_instance_group is an unmanaged, zonal instance group; a managed group is the separate google_compute_instance_group_manager resource.
• Member instances belong in the instances list; if Terraform omits them it will try to detach instances that are currently members.
• named_port blocks must match what the backend service expects, or load balancing breaks after apply.
• Do not import an instance group that is actually managed by a MIG; manage it through the group manager and its instance template instead.

Doing it manually with terraform import

The native approach is to write the google_compute_instance_group block by hand, then run terraform import google_compute_instance_group.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 Google Cloud resources