F35 Change: Build Fedora Cloud Images with Hybrid BIOS+UEFI Boot Support (System-Wide Change)

[Ben Cotton]

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

== Summary ==

With recent changes in public cloud widely accepting the
use of UEFI boot, it would be consistent to add hybrid boot in support of
both unifying the legacy (BIOS) and UEFI boot to the Fedora Linux
cloud base images.

== Owner ==

* Name: [[User:Davdunc|David Duncan]], [[User:Chrismurphy|Chris
Murphy]], [[User:Salimma|Michel Alexandre Salim]],
[[User:Dcavalca|Davide Cavalca]], [[User:Ngompa|Neal Gompa]],
[[User:Dustymabe|Dusty Mabe]]
* Email: [e-mail], [e-mail],
[e-mail], [e-mail], [e-mail],
[e-mail]
* Products: Fedora Cloud Edition
* Responsible WGs: Fedora Cloud WG

== Detailed Description ==
The Fedora Cloud Edition image will be updated to be configured with
multiple partitions and a GPT label instead of one single partition
and implicit MBR.

The partition order will be:

# A BIOS boot partition
# An EFI System partition
# A general data partition

== Benefit to Fedora ==

This is a continuation from the changes outlined in the
[[Releases/34|Fedora Linux 34]] changes to
[[Changes/UnifyGrubConfig|unify the Grub configuration files]]. There
has been an overwhelming support in the public cloud architectures
leading to widespread support for UEFI boot in support of migration
work. This also adds support for other anticipated changes that would
require this modification to include the boot partitions; both legacy
boot as a fallback through the BIOS boot partition and UEFI boot
through the EFI system partition. This is going to require a group of
modifications to the cloud base, including modifying the partition to
support UEFI and a disk label change to GPT. With this change in
place, the images will have greater flexibility to support file
systems, such as btrfs, for boot across a number of supported
providers and environments.

* To have a consistent configuration across all the architectures
* Allows the same image to be booted using either UEFI or legacy BIOS.
* Allow easier migration from one environment to another where there
is potentially a change in boot loader.
* Use the same documentation and commands for the available cloud
architectures instead of having special cases for different
environments.
* Align with images generated by COSA, KIWI, and OSBuild on how the
GRUB configuration files are used.
* Align with other installation methods on how the partitions under
<code>/boot</code> are defined
* Align with other distributions, like CentOS and openSUSE, on support
for GRUB configuration

== Scope ==

* Proposal owners:
** Submit PRs for Cloud Edition kickstarts to produce hybrid boot.
* Release engineering: [https://pagure.io/releng/issue/10143 #10143]
* Policies and guidelines: N/A
* Trademark approval: N/A

== Upgrade/compatibility impact ==

Change will not affect upgrades.

== How To Test ==

Once the change lands in Rawhide, spin up the images in AWS, GCP, and
KVM/OpenStack to test to see systems boot and run. Where possible,
test images on cloud virtual machines types where both boot methods are
supported.

Verify that the general data partition is properly grown in the case
that the root volume is larger than the image default.

== User Experience ==

* Mostly transparent.
* Consistent recovery experience with other distributions and builds
of Fedora Linux.

== Dependencies ==

* fedora-kickstarts

== Documentation ==

No extra documentation is required reading for users. Supporting
recovery documentation is already available.

== Release Notes ==

Fedora Linux cloud images are updated to boot both UEFI and legacy
boot (BIOS) through a hybrid configuration.