Bazel rules for OCI containers

This is an alternative to rules_docker.

We start from first principles and avoided some pitfalls we learned in maintaining that repo:

Use a toolchain consisting of off-the-shelf, pre-built layer and container manipulation tools.
Don't write language-specific rules, as we cannot be experts on all languages, nor can users deal with the versioning issues that come with dependencies we would be forced to take on the rules for those languages.
Don't be docker-specific, now that it has a commercial license and other container runtimes exist (podman for example).
Use our toolchain hermetically: don't assume there is a docker pre-installed on the machine.
Keep a tight complexity budget for the project so we are able to commit to effective maintenance.

Need help? This ruleset has support provided by https://aspect.dev.

Installation

From the release you wish to use: https://github.com/bazel-contrib/rules_oci/releases copy the WORKSPACE snippet into your WORKSPACE file.

To use a commit rather than a release, you can point at any SHA of the repo.

For example to use commit abc123:

Replace url = "https://github.com/bazel-contrib/rules_oci/releases/download/v0.1.0/rules_oci-v0.1.0.tar.gz" with a GitHub-provided source archive like url = "https://github.com/bazel-contrib/rules_oci/archive/abc123.tar.gz"
Replace strip_prefix = "rules_oci-0.1.0" with strip_prefix = "rules_oci-abc123"
Update the sha256. The easiest way to do this is to comment out the line, then Bazel will print a message with the correct value.

Note that GitHub source archives don't have a strong guarantee on the sha256 stability, see https://github.blog/2023-02-21-update-on-the-future-stability-of-source-code-archives-and-hashes

Usage

rules_oci does not contain language-specific rules, but we do document how to accomplish typical tasks, and migrate from the language-specific rules in rules_docker.

Go: Docs
JavaScript: Docs
WASM: Example

Your language not listed above? See bazel-contrib#55

There are more examples of usage in the examples folder. Note that the examples rely on the setup code in the /WORKSPACE file in the root of this repo.

Choosing between zot or crane as the local registry

rules_oci supports two different registry implementation for the temporary storage within actions spawned by bazel. By default we recommend using zot as it stores blobs on disk and is memory efficient but doesn't support Docker images. On the other hand, crane is memory hungry as it stores blobs in memory leading to high memory usage but crane supports both OCI and Docker images which is quite useful for using Docker images pulled from the registries such as Docker Hub.

Public API

Construct image layers

oci_image Build an OCI compatible container image.
oci_image_index Build a multi-architecture OCI compatible container image.
oci_tarball Creates tarball from oci_image that can be loaded by runtimes.

Pull and Push

oci_pull Pulls image layers using Bazel's downloader.
oci_push Push an oci_image or oci_image_index to a remote registry.

Testing

structure_test Test rule running container_structure_test against an oci_image.

Signing

cosign_sign Sign an oci_image using cosign binary at a remote registry.
cosign_attest Add an attachment to an oci_image at a remote registry using cosign.

LavaToaster / rules_oci