Changes/OstreeNativeContainer

ostree native containers / CoreOS layering

Summary

Enhance the (rpm-)ostree stack to natively support OCI/Docker containers as a transport and delivery mechanism for operating system content.

This is the basis of https://github.com/coreos/enhancements/blob/main/os/coreos-layering.md

Owner

• Name: Colin Walters

• Email: walters@verbum.org

Current status

Significant code has been written and is shipping - you can try this today! You need at least rpm-ostree v2021.14 and skopeo 1.5.1

• Targeted release: Fedora Linux 36
• Last updated: 2021-12-01
• devel thread
• FESCo issue: #2704
• Tracker bug: <will be assigned by the Wrangler>
• Release notes tracker: <will be assigned by the Wrangler>

Detailed Description

Having the Fedora ecosystem (from users to release engineering) maintain tooling that operates on all three of "container images", RPMs, and OSTree updates is a maintenance burden.

This proposes that:

• The ostree stack is enhanced to support encapsulating/unencapsulating ostree commits as OCI/Docker images (DONE)
• rpm-ostree is updated to consume this, while still supporting all its current features (e.g. per-machine package layering) (DONE)
• We ship e.g. quay.io/fedora/coreos:stable and quay.io/fedora/silverblue:36 etc.
• We support deriving new user custom images from these images
• We enhance this tooling to support chunking

For more details, please see:

• CoreOS layering enhancement
• rpm-ostree container docs
• ostree-rs-ext project

Note that significant effort has been invested in ensuring compatibility between what exists in ostree today and OCI/Docker container image "encapsulation". For example, we will continue to reuse the GPG signature infrastructure on OSTree commits that exists today - the ostree tooling knows how to verify the signature *inside* the container image. In the future, we will also likely invest in container-native signatures.

Benefit to Fedora

• Stronger focus on Docker/OCI as transport for operating system and applications
• New ability to easily create derived operating system images "server side"
• More benefit from e.g. work on container deltas

Scope

• Proposal owners:

Lots of detailed items listed in the rpm-ostree/CoreOS docs.

• Other developers: The "other" here is vague, but certainly developing this so far has needed cooperation with e.g. the containers/ organization etc.

• Release engineering: https://pagure.io/releng/issue/10399

• Policies and guidelines: N/A (not needed for this Change)

• Trademark approval: N/A (not needed for this Change)

• Alignment with Objectives: No

Upgrade/compatibility impact

Each individual edition/spin would need to choose when and how to make a cutover to containers as a transport. The Fedora OSTree repository would continue to be maintained until that is finished.

How To Test

See the examples under https://coreos.github.io/rpm-ostree/container/

User Experience

Users of rpm-ostree systems will primarily interact with container images.

Dependencies

Release engineering.

Contingency Plan

• Contingency mechanism: Continue to ship updates via baseline OSTree
• Blocks release? No

Documentation

Already linked above to avoid duplicating it here.