Add support for oci format for disk images

[schaefi]

The oci:... format is a special case that allows you to create an OCI-compliant container from a specified reference container. The created container image has the actual disk image added as a new layer. The specification of the oci:image_format:container_transport format contains two parts separated by a colon. The first part specifies one of the above disk formats or just "raw" if the disk should be stored as raw disk inside of the container. The second part specifies one of the supported skopeo container transport formats, for details see the skopeo man page. This format is particularly useful for building an image which bundles the actual disk image and its runtime requirements into one artifact.

[schaefi]

I saw several people running VMs from containers, e.g. the anaconda build process running a boxbuild in a container. There are also other use cases from users who bundle the actual runtime for a VM in a container. I find this really useful and want to support the building of such images in a native way by adding a new format type for disk images.

[Conan-Kudo]

So I'm a little confused, is this wrapping a disk image as an OCI archive artifact to push into a registry?

[schaefi]

So I'm a little confused, is this wrapping a disk image as an OCI archive artifact to push into a registry?

yes you can do that as well. It would however also be possible to specify a <containerconfig> element and place an entry command which starts the disk image via e.g qemu when you launch the container. So several use cases are possible.

The integration test only does what you described though. The integration test uses the super small alpine container as a reference container, places the built disk image into it and creates a new container as an additional layer to the base. The result is basically only useful as a data container to push to some registry. But you could also think of using the latest qemu container instead of alpine and add the image to this reference. So you would bundle the runtime with the VM image and could launch it when you start the container instance... and maybe more