LIBDNF5 OCI Plugin

This, experimental!, project enables consuming YUM repositories stored in an OCI registry. It currently serves as a proof of concept for the native OCI storage for DNF proposal.

As experiments go, the code in this git repository is written in bash simply because it is simple to get started. If/when it is decided to move towards production-grade, it must obviously be re-written in a more suitable technology.

In reality, the content of this git repository don't necessarily implement a plugin. Instead, it provides a set of scripts that are used in conjunction with the Actions LIBDNF5 Plugin.

How does it work?

The plugin ties into two hooks of the DNF5 Workflow to preempt OCI requests, making content available locally instead. The oci.actions file defines these connections.

The first hook is the repos_configured. The plugin iterates through all the enabled YUM repositories, finds the ones where baseurl use the oci:// protocol, and fetches the repodata for that image reference. The repodata is stored in the DNF cache. Additionally, metadata is also stored in the cache to avoid unnecessary requests to the OCI registry and to make certain information available for the next hook. The plugin modifies the YUM repository configuration (the one in memory, not on disk), to replace the value of baseurl with a file:// URL pointing to the DNF cache for that particular YUM repository.

Next, the goal_resolved hook is used to download each of the RPMs marked for installation from OCI to the DNF cache directory.

From DNF's perspective, it is installing RPMs from a local YUM repository.

Installing it

If you want to try this out (have I mentioned this is experimental?!?):

1. Install the actions plugin: sudo dnf install libdnf5-plugin-actions.

2. Install oras: sudo dnf install golang-oras.

3. Install yq: sudo dnf install yq.

4. Add oci_repos_configured.sh and oci_goal_resolved.sh somewhere in the root user's PATH, e.g.:

   sudo ln -s `pwd`/oci*.sh /usr/local/bin/

5. Link the actions file:

   sudo ln -s `pwd`/oci.actions /etc/dnf/libdnf5-plugins/actions.d/

That should be sufficient.

If you have gotten this far, you are likely interested in actually using the plugin. You can place the following YUM repo file under /etc/yum.repos.d/:

[oci-repo-test]
name=oci-repo-test
baseurl=oci://quay.io/lucarval/yum-repo:latest
enabled=1
gpgcheck=1

The repository contains cowsay and lolcat.