---
description: |
  You can create or modify custom plugins to support HCP Packer. Add support for HCP Packer to let plugins manage image metadata stored in the HCP Packer registry.
page_title: Enable HCP Packer support for custom plugins
---

# Enable HCP Packer Support for Custom Plugins

This page explains how to update a custom plugin so that it can publish image metadata to the [HCP Packer registry](/hcp/docs/packer). Refer to [Custom Builders](/packer/docs/plugins/creation/custom-builders) and [Custom Post-Processors](/packer/docs/plugins/creation/custom-post-processors) for details about creating an external Packer plugin.

Before pushing metadata to the HCP Packer registry, Packer uses the [`par.artifact.metadata` key](https://pkg.go.dev/github.com/hashicorp/packer-plugin-sdk/packer/registry/image#pkg-constants)
to query a builder artifact for the image metadata that a particular component would like to have stored in the registry.

For details and examples of how to manage image metadata, refer to the [HCP Packer GitHub documentation](https://pkg.go.dev/github.com/hashicorp/packer-plugin-sdk/packer/registry/image).

HCP Packer is under active development, and we suggest plugin maintainers to keep up with the SDK changes for more on HCP Packer support.

## Builder Artifact

To support HCP Packer, changes must be made to the plugin's build artifact. The artifact should keep the appropriate
Image metadata in state under the key `par.artifact.metadata`. The expected key is provided by the [image.ArtifactStateURI](https://pkg.go.dev/github.com/hashicorp/packer-plugin-sdk/packer/registry/image#pkg-constants) constant.

To make HCP Packer support easier, we ship an Image package with the [packer-plugin-sdk](https://pkg.go.dev/github.com/hashicorp/packer-plugin-sdk/packer/registry/image#pkg-overview).
We provide the [`FromArtifact`](https://pkg.go.dev/github.com/hashicorp/packer-plugin-sdk/packer/registry/image#FromArtifact) function
to easily create an Image with the basic information contained in the Artifact. If customization is necessary, the `FromArtifact` accepts
override functions as the second argument, and that can be used to set different values for the metadata.

The [Image metadata](https://pkg.go.dev/github.com/hashicorp/packer-plugin-sdk/packer/registry/image#Image) must contain every
metadata HCP Packer should store about this component. The structure is:
```go
// Image represents the metadata for some Artifact in the HCP Packer Registry.
type Image struct {
	// ImageID is a unique reference identifier stored on the HCP Packer registry
	// that can be used to get back the built artifact of a builder or post-processor.
	ImageID string
	// ProviderName represents the name of the top level cloud or service where the built artifact resides.
	// For example "aws, azure, docker, gcp, and vsphere".
	ProviderName string
	// ProviderRegion represents the location of the built artifact.
	// For cloud providers region usually maps to a cloud region or zone, but for things like the file builder,
	// S3 bucket or vsphere cluster region can represent a path on the upstream datastore, or cluster.
	ProviderRegion string
	// Labels represents additional details about an image that a builder or post-processor may with to provide for a given build.
	// Any additional metadata will be made available as build labels within a HCP Packer registry iteration.
	Labels map[string]string
	// SourceImageID is the cloud image ID of the image that was used as the
	// source for this image. If set, the HCP Packer registry will be able
	// link the parent and child images for ancestry visualizations and
	// dependency tracking.
	SourceImageID string
}
```

Where `ImageID`, `ProviderName`, and `SourceImageID` are mandatory fields.

Examples using the `FromArtifact` method:

- Simple form:
```go
func (a *Artifact) State(name string) interface{} {
	if name == registryimage.ArtifactStateURI {
		img, err := registryimage.FromArtifact(a)
		if err != nil {
			log.Printf("[DEBUG] error encountered when creating a registry image %v", err)
			return nil
		}
	  return img
	}
	return a.StateData[name]
}
```

- Using overrides:
```go
func (a *Artifact) State(name string) interface{} {
	if name == registryimage.ArtifactStateURI {
		img, err := registryimage.FromArtifact(a,
                registryimage.WithID(a.Name),
                registryimage.WithRegion(a.Region.Name()),
                registryimage.WithProvider("happy-cloud"),
                registryimage.WithSourceID(a.SourceID),
                registryimage.SetLabels(a.Labels),
              )
		if err != nil {
			log.Printf("[DEBUG] error encountered when creating a registry image %v", err)
			return nil
		}
	  return img
	}
	return a.StateData[name]
}
```

See [packer-plugin-sdk/packer/registry/image](https://pkg.go.dev/github.com/hashicorp/packer-plugin-sdk/packer/registry/image#pkg-examples) for additional examples.

### SDK Version

- The HCP Packer support is available from packer-plugin-sdk >= v0.2.7

## Plugins Example

The following plugins currently support HCP Packer and are great references for development:

- [packer-plugin-amazon](https://github.com/hashicorp/packer-plugin-amazon)
- [packer-plugin-azure](https://github.com/hashicorp/packer-plugin-azure)
- [packer-plugin-vsphere](https://github.com/hashicorp/packer-plugin-vsphere)
- [packer-plugin-docker](https://github.com/hashicorp/packer-plugin-docker)
- [packer-plugin-googlecompute](https://github.com/hashicorp/packer-plugin-googlecompute)

## HCP Packer

Refer to the following resources to learn about HCP Packer:

- [HCP Packer documentation](/hcp/docs/packer) 
- [HCP Packer tutorials](/packer/tutorials/hcp-get-started).
- [Log into the HCP portal](https://portal.cloud.hashicorp.com)