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 ==
Improve support for unified kernels in Fedora.
== Owner ==
* Name: [[User:kraxel| Gerd Hoffmann]]
* Email: kra...@redhat.com
* Name: [[User:vittyvk| Vitaly Kuznetsov]]
* Email: vkuzn...@redhat.com
== Detailed Description ==
See [[ Changes/Unified_Kernel_Support_Phase_1 ]] for overview and Phase 1 goals.
Phase 2 goals
* Add support for booting UKIs directly.
** Boot path is shim.efi -> UKI, without any boot loader (grub,
sd-boot) involved.
** The UEFI boot configuration will get an entry for each kernel installed.
** Newly installed kernels are configured to be booted once (via BootNext).
** Successful boot of the system will make the kernel update permanent
(update BootOrder).
* Enable UKIs for aarch64.
** Should be just flipping the switch, dependencies such as kernel
zboot support are merged.
* Add a UEFI-only cloud image variant which uses UKIs.
** Also suitable for being used in confidential VMs.
** Cover both x86_64 and aarch64.
Related bugs
* shim: remove dependency on grub2-efi-x64
([https://bugzilla.redhat.com/show_bug.cgi?id=2240989 buzilla
2240989])
* shim: handling of multiple lines in BOOT.CSV is inconsistent
([https://issues.redhat.com/browse/RHEL-10704 jira RHEL-10704],
[https://github.com/rhboot/shim/issues/554 github 554])
* anaconda: add support for
[https://www.freedesktop.org/wiki/Specifications/DiscoverablePartitionsSpec/
discoverable partitions]
([https://bugzilla.redhat.com/show_bug.cgi?id=2160074 bugzilla
2160074], [https://bugzilla.redhat.com/show_bug.cgi?id=2178043
bugzilla 2178043])
* dracut: do not create yet another initramfs for UKIs
([https://github.com/dracutdevs/dracut/pull/2521 github PR 2521])
* kernel: enable UKIs on aarch64
([https://gitlab.com/cki-project/kernel-ark/-/merge_requests/2818 MR
2818])
== Feedback ==
== Benefit to Fedora ==
* Better secure boot support: the UKI initrd is covered by the signature.
* Better support for tpm measurements and confidential computing.
** measurements are more useful if we know what hashes to expect for the initrd.
** measurements are more useful without grub.efi in the boot path
(which measures each grub.cfg line processed).
* More robust boot process
** generating the initrd on the installed system is fragile
== Scope ==
* Proposal owners:
** updates for virt-firmware and uki-direct packages.
** enable UKIs on aarch64
([https://gitlab.com/cki-project/kernel-ark/-/merge_requests/2818 MR
2818]).
** prepare kickstart ([https://pagure.io/fedora-kickstarts.git Fedora
kickstarts]) changes for generating UKI enabled images.
* Other developers:
** installer/anaconda: implement discoverable partition support.
** bootloader/shim: fix bugs.
** Fedora Cloud SIG: Add UKI enabled images as an option to
[https://fedoraproject.org/cloud/download Download Fedora Cloud]
** See also:
[https://fedoraproject.org/wiki/Changes/Unified_Kernel_Support_Phase_2#Related_bugs
Related Bugs] section.
* Release engineering: [https://pagure.io/releng/issues #Releng issue number]
* Policies and guidelines: N/A (not needed for this Change)
* Trademark approval: N/A (not needed for this Change)
* Alignment with Objectives:
== Upgrade/compatibility impact ==
None, it's opt-in. Also the uefi cloud image is an additional image
and will not replace the current bios/uefi hybrid image.
== How To Test ==
Switch an existing install to use UKIs.
Needs up-to-date Fedora 39 or Rawhide install in a virtual machine.
Bare metal hardware with standard storage (ahci / nvme) should work too.
Needs an big enough ESP to store UKI images there (minimum 200M,
recommended 500M).
1. dnf install virt-firmware uki-direct
* The uki-direct package contains the kernel-install plugin and
systemd unit needed to automatically manage kernel updates.
* You should have version 23.10 or newer.
2. sh
/usr/share/doc/python3-virt-firmware/experimental/fixup-partitions-for-uki.sh
* Workaround for [https://bugzilla.redhat.com/show_bug.cgi?id=2160074
bug 2160074] (anaconda not setting up
[https://www.freedesktop.org/wiki/Specifications/DiscoverablePartitionsSpec/
discoverable partitions]).
* UKIs need this to find the root filesystem without root=... on the
kernel command line.
3. dnf install kernel-uki-virt
4. kernel-bootcfg --show
* optional step, shows UEFI boot configuration, the new UKI should be
added as BootNext
$ kernel-bootcfg --show
# C - BootCurrent, N - BootNext, O - BootOrder
#
# N- 0008 - 6.5.7-300.fc39.x86_64<= entry for
the the new kernel
# C O - 0007 - 6.5.6-300.fc39.x86_64<= currently
running kernel
# O - 0006 - Fedora <= grub2 entry
# O -
