F38 proposal: Build Fedora Silverblue & Kinoite using rpm-ostree unified core mode (Self-Contained Change proposal)

[Ben Cotton]

https://fedoraproject.org/wiki/Changes/FedoraSilverblueUnifiedCore

This document represents a proposed Change. As part of the Changes
process, proposals are publicly announced in order to receive
community feedback. This proposal will only be implemented if approved
by the Fedora Engineering Steering Committee.

== Summary ==

rpm-ostree upstream development is focusing on the "unified core" mode
and the previous mode is being deprecated. Fedora Silverblue and
Fedora Kinoite are currently building using the old mode and we've
wanted to move over for a while. The main advantage of the unified
core mode is that it is stricter and safer, while enabling some post
processing steps to happen during or after the image build.

== Owner ==

* Name: [[User:Siosm| Timothée Ravier]], [[User:Tpopela| Tomáš
Popela]], [[User:Walters| Colin Walters]]
* Email: <siosm(a)fedoraproject.org&gt;. <tpopela(a)fedoraproject.org&gt;,
<walters(a)fedoraproject.org&gt;


== Detailed Description ==

For more details about the difference between the two mode, you can
read the upstream issue:
https://github.com/coreos/rpm-ostree/issues/729. See also the history
in https://pagure.io/workstation-ostree-config/issue/137.

On top of the advantages listed above, we need unified core support to
be able to add bootupd integration to Fedora Silverblue & Kinoite.
See:
* https://fedoraproject.org/wiki/Changes/FedoraSilverblueBootupd
* https://github.com/fedora-silverblue/issue-tracker/issues/120
* https://pagure.io/workstation-ostree-config/pull-request/313

The in-progress changes are in:
* Support in Pungi: https://pagure.io/pungi/pull-request/1626 &
https://pagure.io/pungi/pull-request/1629
* Fedora Pungi configuration change:
https://pagure.io/pungi-fedora/pull-request/1115
* Fedora Silverblue & Kinoite changes in progress in:
https://pagure.io/workstation-ostree-config/pull-request/296

GitHub issue used to track this work and testing:
https://github.com/fedora-silverblue/issue-tracker/issues/333

== Feedback ==

None yet.

<!-- Summarize the feedback from the community and address why you
chose not to accept proposed alternatives. This section is optional
for all change proposals but is strongly suggested. Incorporating
feedback here as it is raised gives FESCo a clearer view of your
proposal and leaves a good record for the future. If you get no
feedback, that is useful to note in this section as well. For
innovative or possibly controversial ideas, consider collecting
feedback before you file the change proposal. -->

== Benefit to Fedora ==

The old mode in rpm-ostree is not maintained anymore and less tested
thus more prone to bugs. Moving to the new mode will unify Silverblue
& Kinoite to the same code that is used to build Fedora CoreOS and
that receives a lot of testing. This will remove maintenance burden on
the rpm-ostree project as they will thus be able to remove the old
code. The new mode also makes composes work the same on the server
side and the client side and makes them safer by more strictly
confining scriptlets execution.

== Scope ==

* Proposal owners: Testing of builds with the new mode to make sure
there is not regression. The infra & configurations changes for Pungi
should be ready.
* Other developers: N/A
* Release engineering: N/A
* Policies and guidelines: N/A (not needed for this Change)
* Trademark approval: N/A (not needed for this Change)

* Alignment with Objectives: N/A

== Upgrade/compatibility impact ==

There should be not visible change for users when upgrading. The
change only impacts the way the images are composed on the server.

== How To Test ==

Use the commands from the justfile in
https://pagure.io/workstation-ostree-config/pull-request/296 to test
building in unified core mode. Update an existing installation and
verify that everything works as expected. Once we merge that in
Rawhide, updating will be enough (no need to rebuild).

== User Experience ==

N/A

== Dependencies ==

N/A

== Contingency Plan ==

* Contingency mechanism: Revert to non unified core build mode (single
change in Fedora's Pungi configuration). Owners will do it. Nothing to
do for users.
* Contingency deadline: Can happen anytime.
* Blocks release? No

== Documentation ==

N/A

== Release Notes ==

N/A


-- 
Ben Cotton
He / Him / His
Fedora Program Manager
Red Hat
TZ=America/Indiana/Indianapolis