From Fedora Project Wiki

Build Fedora Cloud Images with Hybrid Boot Support

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

Current status

  • Targeted release: Fedora Linux 35
  • Last Updated: 2021-06-03
  • FESCo Issue: <will be assigned by the Wrangler>
  • Tracker bug: <will be assigned by the Wrangler>
  • Release notes tracker: <will be assigned by the Wrangler>

Detailed Description

The cloud base will be created with multiple partitions and a GPT label instead of one single partition and implicit MBR.

The partition order will be:

  1. A BIOS boot partition
  2. An EFI System partition
  3. A general data partition

Feedback

Benefit to Fedora

This is a continuation from the changes outlined in the Fedora Linux 34 changes to unify the Grub configuration files. There has been an overwhelming support in the public cloud architectures leading to widespread support for UEFI boot to support migration work. This also add support for other anticipated changes which 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 /boot 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:
  • 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.

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