registry-image-resource

Registry Image Resource

Supports checking, fetching, and (eventually) pushing of images to Docker registries.

This resource is intended as a replacement for the Docker Image resource. Here are the key differences:

• This resource is implemented in pure Go and does not use the Docker daemon or CLI.
• Therefore, it does not need to run privileged, and should be much more efficient. It will also be less error-prone (parsing docker CLI output was janky).
• This resource does not support building. This should instead be done with a task. Using Kaniko would be a great idea!
• A goal of this resource is to stay as small and simple as possible. The Docker Image resource grew way too large and complicated. Initially, it this resource is designed solely to support being used to fetch images for Concourse containers (using image_resource and resource_types).
  • This may need to expand later on as it would be completely reasonable to implement put here, so we may need to be able to get in a different format in order to be symmetrical.
• This resource has stronger test coverage.

Source Configuration

• repository: Required. The name of the repository, e.g. alpine.
• tag: Optional. Default latest. The name of the tag to monitor.
• debug: Optional. Default false. If set, progress bars will be disabled and debugging output will be printed instead.

Behavior

check: Discover new digests.

Reports the current digest that the registry has for the given tag.

in: Fetch the image's rootfs and metadata.

Parameters

• format: Optional. Default rootfs. The format to fetch as. (See below.)

Formats

rootfs

The rootfs format will fetch and unpack the image for use by Concourse task and resource type images.

This the default for the sake of brevity in pipelines and task configs.

In this format, the resource will produce the following files:

• rootfs/...: the unpacked rootfs produced by the image.
• metadata.json: the runtime information to propagate to Concourse.

oci

The oci format will fetch the image and write it to disk in OCI format. This is analogous to running docker save.

In this format, the resource will produce the following files:

• image.tar: the OCI image tarball, suitable for passing to docker load.

out: Push an image up to the registry under the given tags.

Not implemented yet. Once implemented, this may take an image in a standard format (say, whatever docker save does) and upload it to the registry to the tag configured in source.