What are the (current) requirements for producing a bootc compatible base container image?

[miabbott]

This came up in discussions at an internal F2F...what is required to produce a boot compatible base container image?

The conversations I had seemed to indicate a requirement on the content of the container image (i.e. including kernel and bootc), but also how the container image was produced.

• Do we require users to produce base container images via rpm-ostree compose image?
• Can users create a base container image by using ostree container encapsulate on an existing ostree commit?
• Does the ostree commit need to be generated using "unified core" mode?

cc: @runcom @travier

[travier]

As we want bootc images to have support for bootupd, we need the images to be built using unified core mode.

If we want to remove that dependency (but I don't think we should), then this is coreos/bootupd#441.

Thus while technically an rpm-ostree compose tree --unified-core=true + ostree container encapsulate should work, I think we should standardize on rpm-ostree compose image being the only supported option to build bootc base images.

[vrothberg]

I like that idea.

Once the conversation has settled, please make sure that the (current) recommended way of building base images is documented.

[runcom]

I think this is here https://containers.github.io/bootc/bootc-images/#building-bootc-compatible-base-images (except the standardization and a warning that osbuild is not producing unified-core/bootupd compatible images)

[miabbott]

Heh, I wrote those docs 😄

I started this discussion to confirm those assumptions and get better clarity.

We have places in the docs where we allude to non-ostree backends in the future...should that be a factor in how we define what a bootc base image is? Or just address the reality of today?

[travier]

From my perspective, while we may plan for a future where we don't have ostree at all anymore, right now, it's still there, so we should mention it as it helps understand what's going on.

[cgwalters]

#215 will change this to "almost none".