---
description: |
  The googlecompute Packer builder is able to create images for use with Google
  Cloud Compute Engine (GCE) based on existing images.
layout: docs
page_title: Google Compute - Builders
sidebar_title: Google Cloud
---

# Google Compute Builder

Type: `googlecompute`

The `googlecompute` Packer builder is able to create
[images](https://developers.google.com/compute/docs/images) for use with
[Google Compute Engine](https://cloud.google.com/products/compute-engine) (GCE)
based on existing images.

It is possible to build images from scratch, but not with the `googlecompute`
Packer builder. The process is recommended only for advanced users, please see
[Building GCE Images from Scratch](https://cloud.google.com/compute/docs/tutorials/building-images)
and the [Google Compute Import
Post-Processor](/docs/post-processors/googlecompute-import) for more
information.

## Authentication

Authenticating with Google Cloud services requires at most one JSON file,
called the _account file_. The _account file_ is **not** required if you are
running the `googlecompute` Packer builder from a GCE instance with a
properly-configured [Compute Engine Service
Account](https://cloud.google.com/compute/docs/authentication).

### Running With a Compute Engine Service Account

If you run the `googlecompute` Packer builder from a GCE instance, you can
configure that instance to use a [Compute Engine Service
Account](https://cloud.google.com/compute/docs/authentication). This will allow
Packer to authenticate to Google Cloud without having to bake in a separate
credential/authentication file.

To create a GCE instance that uses a service account, provide the required
scopes when launching the instance.

For `gcloud`, do this via the `--scopes` parameter:

```shell-session
$ gcloud compute instances create INSTANCE-NAME \
  --project YOUR_GCP_PROJECT \
  --image-family ubuntu-1804-lts \
  --image-project gce-uefi-images \
  --network YOUR_GCP_NETWORK \
  --zone YOUR_GCP_ZONE \
  --scopes "https://www.googleapis.com/auth/compute,https://www.googleapis.com/auth/devstorage.full_control"
```

For the [Google Developers Console](https://console.developers.google.com):

1.  Choose "Show advanced options"
2.  Tick "Enable Compute Engine service account"
3.  Choose "Read Write" for Compute
4.  Choose "Full" for "Storage"

**The service account will be used automatically by Packer as long as there is
no _account file_ specified in the Packer configuration file.**

### Running Without a Compute Engine Service Account

The [Google Developers Console](https://console.developers.google.com) allows
you to create and download a credential file that will let you use the
`googlecompute` Packer builder anywhere. To make the process more
straightforwarded, it is documented here.

1.  Log into the [Google Developers
    Console](https://console.developers.google.com) and select a project.

2.  Under the "API Manager" section, click "Credentials."

3.  Click the "Create credentials" button, select "Service account key"

4.  Create a new service account that at least has
    `Compute Engine Instance Admin (v1)` and `Service Account User` roles.

5.  Choose `JSON` as the Key type and click "Create". A JSON file will be
    downloaded automatically. This is your _account file_.

### Precedence of Authentication Methods

Packer looks for credentials in the following places, preferring the first
location found:

1.  An `account_file` option in your packer file.

2.  A JSON file (Service Account) whose path is specified by the
    `GOOGLE_APPLICATION_CREDENTIALS` environment variable.

3.  A JSON file in a location known to the `gcloud` command-line tool.
    (`gcloud auth application-default login` creates it)

    On Windows, this is:

        %APPDATA%/gcloud/application_default_credentials.json

    On other systems:

        $HOME/.config/gcloud/application_default_credentials.json

4.  On Google Compute Engine and Google App Engine Managed VMs, it fetches
    credentials from the metadata server. (Needs a correct VM authentication
    scope configuration, see above.)

## Examples

### Basic Example

Below is a fully functioning example. It doesn't do anything useful since no
provisioners or startup-script metadata are defined, but it will effectively
repackage an existing GCE image. The account_file is obtained in the previous
section. If it parses as JSON it is assumed to be the file itself, otherwise,
it is assumed to be the path to the file containing the JSON.

```json
{
  "builders": [
    {
      "type": "googlecompute",
      "account_file": "account.json",
      "project_id": "my project",
      "source_image": "debian-7-wheezy-v20150127",
      "ssh_username": "packer",
      "zone": "us-central1-a"
    }
  ]
}
```

### Windows Example

Before you can provision using the winrm communicator, you need to allow
traffic through google's firewall on the winrm port (tcp:5986). You can do so
using the gcloud command.

    gcloud compute firewall-rules create allow-winrm --allow tcp:5986

Or alternatively by navigating to [https://console.cloud.google.com/networking/firewalls/list](https://console.cloud.google.com/networking/firewalls/list).

Once this is set up, the following is a complete working packer config after
setting a valid `account_file` and `project_id`:

```json
{
  "builders": [
    {
      "type": "googlecompute",
      "account_file": "account.json",
      "project_id": "my project",
      "source_image": "windows-server-2016-dc-v20170227",
      "disk_size": "50",
      "machine_type": "n1-standard-1",
      "communicator": "winrm",
      "winrm_username": "packer_user",
      "winrm_insecure": true,
      "winrm_use_ssl": true,
      "metadata": {
        "windows-startup-script-cmd": "winrm quickconfig -quiet & net user /add packer_user & net localgroup administrators packer_user /add & winrm set winrm/config/service/auth @{Basic=\"true\"}"
      },
      "zone": "us-central1-a"
    }
  ]
}
```

-> **Warning:** Please note that if you're setting up WinRM for provisioning, you'll probably want to turn it off or restrict its permissions as part of a shutdown script at the end of Packer's provisioning process. For more details on the why/how, check out this useful blog post and the associated code:
https://cloudywindows.io/post/winrm-for-provisioning-close-the-door-on-the-way-out-eh/

This build can take up to 15 min.

### Nested Hypervisor Example

This is an example of using the `image_licenses` configuration option to create
a GCE image that has nested virtualization enabled. See [Enabling Nested
Virtualization for VM
Instances](https://cloud.google.com/compute/docs/instances/enable-nested-virtualization-vm-instances)
for details.

```json
{
  "builders": [
    {
      "type": "googlecompute",
      "account_file": "account.json",
      "project_id": "my project",
      "source_image_family": "centos-7",
      "ssh_username": "packer",
      "zone": "us-central1-a",
      "image_licenses": ["projects/vm-options/global/licenses/enable-vmx"]
    }
  ]
}
```

## Configuration Reference

Configuration options are organized below into two categories: required and
optional. Within each category, the available options are alphabetized and
described.

In addition to the options listed here, a
[communicator](/docs/templates/communicator) can be configured for this
builder.

### Required:

@include 'builder/googlecompute/Config-required.mdx'

### Optional:

@include 'builder/googlecompute/Config-not-required.mdx'

@include 'builder/googlecompute/IAPConfig-not-required.mdx'

## Startup Scripts

Startup scripts can be a powerful tool for configuring the instance from which
the image is made. The builder will wait for a startup script to terminate. A
startup script can be provided via the `startup_script_file` or
`startup-script` instance creation `metadata` field. Therefore, the build time
will vary depending on the duration of the startup script. If
`startup_script_file` is set, the `startup-script` `metadata` field will be
overwritten. In other words, `startup_script_file` takes precedence.

The builder does not check for a pass/fail/error signal from the startup
script, at this time. Until such support is implemented, startup scripts should
be robust, as an image will still be built even when a startup script fails.

### Windows

A Windows startup script can only be provided via the
`windows-startup-script-cmd` instance creation `metadata` field. The builder
will _not_ wait for a Windows startup script to terminate. You have to ensure
that it finishes before the instance shuts down.

### Logging

Startup script logs can be copied to a Google Cloud Storage (GCS) location
specified via the `startup-script-log-dest` instance creation `metadata` field.
The GCS location must be writeable by the credentials provided in the builder
config's `account_file`.

## Gotchas

CentOS and recent Debian images have root ssh access disabled by default. Set
`ssh_username` to any user, which will be created by packer with sudo access.

The machine type must have a scratch disk, which means you can't use an
`f1-micro` or `g1-small` to build images.
