Create a VM that uses a user-managed service account

This document explains how to create a virtual machine (VM) instance that is configured to use a user-managed service account. A service account is a special kind of account typically used by an application or compute workload to make authorized API calls.

Service accounts are needed for scenarios where a workload, such as a custom application, needs to access Google Cloud resources or perform actions without end-user involvement. For more information about when to use service accounts, see Best practices for using service accounts.

If you have applications that need to make calls to Google Cloud APIs, Google recommends that you attach a user-managed service account to the VM on which the application or workload is running. Then, you grant the service account IAM roles, which gives the service account–and, by extension, applications running on the VM–access to Google Cloud resources.

Before you begin

• If you haven't already, then set up authentication. Authentication is the process by which your identity is verified for access to Google Cloud services and APIs. To run code or samples from a local development environment, you can authenticate to Compute Engine by selecting one of the following options:
  

  Select the tab for how you plan to use the samples on this page:

  Console

  When you use the Google Cloud console to access Google Cloud services and APIs, you don't need to set up authentication.

  gcloud

  1. Install the Google Cloud CLI, then initialize it by running the following command:

     gcloud init

  2. Set a default region and zone.

  Terraform

  To use the Terraform samples on this page in a local development environment, install and initialize the gcloud CLI, and then set up Application Default Credentials with your user credentials.

  1. Install the Google Cloud CLI.

  2. To initialize the gcloud CLI, run the following command:

     gcloud init

  3. If you're using a local shell, then create local authentication credentials for your user account:

     gcloud auth application-default login

     You don't need to do this if you're using Cloud Shell.

  For more information, see Set up authentication for a local development environment.

  REST

  To use the REST API samples on this page in a local development environment, you use the credentials you provide to the gcloud CLI.

  Install the Google Cloud CLI, then initialize it by running the following command:

  gcloud init

  For more information, see Authenticate for using REST in the Google Cloud authentication documentation.

Required roles

To get the permissions that you need to create VMs that use service accounts, ask your administrator to grant you the following IAM roles on the project:

• Compute Instance Admin (v1) (roles/compute.instanceAdmin.v1)
• Create Service Accounts (roles/iam.serviceAccountCreator)

For more information about granting roles, see Manage access to projects, folders, and organizations.

These predefined roles contain the permissions required to create VMs that use service accounts. To see the exact permissions that are required, expand the Required permissions section:

You might also be able to get these permissions with custom roles or other predefined roles.

Overview

It is recommended that you configure service accounts for your VMs as follows:

1. Create a new user-managed service account rather than using the Compute Engine default service account, and grant IAM roles to that service account for only the resources and operations that it needs.
2. Attach the service account to your VM.
3. Set the cloud platform (https://www.googleapis.com/auth/cloud-platform) scope on your VM. This allows the VM's service account to call the Google Cloud APIs that it has permission to use.
   • If you specify the service account by using the Google Cloud console, the VM's access scope automatically defaults to the cloud-platform scope.
   • If you specify the service account by using the Google Cloud CLI or Compute Engine API, you can use the scopes parameter to set the access scope.

Set up a service account

Create a service account and assign the required IAM roles. Assign as many or as little IAM roles as needed. You can modify the IAM roles on your service account as needed.

Google recommends that you limit the privileges of service accounts and regularly check your service account permissions to make sure they are up-to-date.

Use one of the following methods to set up the service account.

resource "google_service_account" "default" {
  account_id   = "service-account-id"
  display_name = "Service Account"
}

Create a VM and attach the service account

After you create the service account, create a VM and attach the service account that you created in the previous section. Also set the VM's access scope to cloud-platform.

If you already have an existing VM and you want to configure that VM to use a different service account, see Change the attached service account.

Use one of the following methods to create a VM and attach the service account.

gcloud compute instances create VM_NAME \
    --service-account=SERVICE_ACCOUNT_EMAIL \
    --scopes=https://www.googleapis.com/auth/cloud-platform

gcloud compute instances create example-vm \
    --service-account [email protected] \
    --scopes=https://www.googleapis.com/auth/cloud-platform

resource "google_compute_instance" "default" {
  name         = "my-test-vm"
  machine_type = "n1-standard-1"
  zone         = "us-central1-a"

  boot_disk {
    initialize_params {
      image = "debian-cloud/debian-11"
    }
  }

  // Local SSD disk
  scratch_disk {
    interface = "SCSI"
  }

  network_interface {
    network = "default"

    access_config {
      // Ephemeral public IP
    }
  }

  service_account {
    # Google recommends custom service accounts with `cloud-platform` scope with
    # specific permissions granted via IAM Roles.
    # This approach lets you avoid embedding secret keys or user credentials
    # in your instance, image, or app code
    email  = google_service_account.default.email
    scopes = ["cloud-platform"]
  }
}

POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/zones/ZONE/instances

{
   "machineType":"zones/MACHINE_TYPE_ZONE/machineTypes/MACHINE_TYPE",
   "name":"VM_NAME",
   
   "disks":[
      {
         "initializeParams":{
            "sourceImage":"projects/IMAGE_PROJECT/global/images/IMAGE"
         },
         "boot":true
      }
   ],
   
   
   "networkInterfaces":[
      {
         "network":"global/networks/NETWORK_NAME"
      }
   ],
   
  "serviceAccounts": [
      {
      "email": "SERVICE_ACCOUNT_EMAIL",
      "scopes": ["https://www.googleapis.com/auth/cloud-platform"]
      }
   ],
   "shieldedInstanceConfig":{
      "enableSecureBoot":"ENABLE_SECURE_BOOT"
   }
}

Access and use other Google Cloud services

After your VM is configured to use the service account, applications can then use the service account to authenticate. The most common method is to authenticate by using Application Default Credentials and a client library. Some Google Cloud tools such as the gcloud CLI are able to automatically use the service account to access Google Cloud APIs from a VM. For more information, see Authenticate workloads using service accounts.

If a service account is deleted, applications will no longer have access to Google Cloud resources through that service account. If you delete the default App Engine and Compute Engine service accounts, your VMs will no longer have access to resources in the project. If you're not sure whether a service account is being used, Google recommends disabling the service account before deleting it. Disabled service accounts can be re-enabled if they are still needed.

Example: Access Cloud Storage resources from your VM

After you have configured your VM to use a service account that has the storage.admin role, you can use tools such as the gcloud CLI to manage files that you have stored on Cloud Storage. To access your Cloud Storage resources, complete the following:

1. Ensure that the service account that is attached to your VM has the roles/storage.admin role.

2. If your VM uses a custom OS image, install the gcloud CLI. By default, the gcloud CLI is installed on most public OS images that are provided by Google Cloud.

3. Connect to the VM.

4. From the VM, use the Google Cloud CLI to manage your Cloud Storage resources.

What's next?

• Learn how to authenticate workloads using service accounts.
• Learn how to change the service account attached to a VM.
• Learn how to list and edit service accounts.
• Review the best practices for working with service accounts and mitigate security risks.