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ostree native containers

For more information on this, see CoreOS layering.

rpm-ostree inherits work in ostree-rs-ext to create “container native ostree” functionality. This elevates OCI/docker containers to be natively supported as a transport mechanism for bootable operating systems.

Rebasing a client system

Use this to switch to booting from a container image:

$ rpm-ostree rebase --experimental ostree-unverified-registry:quay.io/coreos-assembler/fcos:testing-devel

In the near future, we hope to push this more officially to quay.io/fedora/coreos:stable.

However, this model would just be using Docker/OCI transport “on the wire” for content that already exists today. This would aid things like mirroring the OS alongside other container images, but for many users the next step is more interesting:

Using custom builds

The ostree container functionality supports layered container images. See fcos-derivation-example for an example.

This functionality is explicitly experimental; it is unlikely to break booting or anything like that, but the container format or buildsystem may change. For example, see this issue where we may require a command to be run as part of the build in the future.

Creating base images

The ostree-container model creates a bidirectional bridge between ostree and OCI formatted containers. rpm-ostree compose tree today is a tool which natively accepts RPMs (and other content) and outputs an OSTree commit.

This output can be converted into a base image via e.g.:

$ ostree container encapsulate --repo=/path/to/repo fedora/35/x86_64/silverblue docker://quay.io/myuser/fedora-silverblue:35

or:

$ ostree container encapsulate --repo=/path/to/repo fedora/x86_64/coreos/stable oci:/var/tmp/fcos

In the first case, we are pushing to a remote Docker registry, and in the second we are pushing to a local OCI formatted directory. The encapsulate command accepts all the same “transport prefixes” as the skopeo CLI. For more information, see man skopeo.

It is likely at some point that we add rpm-ostree compose container or so which would natively input and output a (base) container image.