From Fedora Project Wiki


Deprecate Legacy BIOS

Summary

Make UEFI a hardware requirement for new Fedora installations on platforms that support it (x86_64). Legacy BIOS support is not removed, but new non-UEFI installation is not supported on those platforms. This is a first step toward eventually removing legacy BIOS support entirely.

Owner

Current status

  • Targeted release: Fedora Linux 37
  • Last updated: 2022-04-26
  • devel thread
  • FESCo issue: #2780
  • Tracker bug: <will be assigned by the Wrangler>
  • Release notes tracker: <will be assigned by the Wrangler>

Detailed Description

UEFI is defined by a versioned standard that can be tested and certified against. By contrast, every legacy BIOS is unique. Legacy BIOS is widely considered deprecated (Intel, AMD, Microsoft, Apple) and on its way out. As it ages, maintainability has decreased, and the status quo of maintaining both stacks in perpetuity is not viable for those currently doing that work.

UEFI originates with Intel, who evolved the spec themselves between 1998 and 2005 before opening it. Because the spec continues to evolve, saying when the "first" UEFI machine shipped is tricky - for instance, we care about many of the capabilities added in 2006, even though machines had already shipped by then, but Tiano (the reference open source implementation, used by at least libvirt/qemu, and originally an Intel project) actually predates that (2004). While perhaps not the first EFI machine, the first machine I can easily find that definitely used it is an Itanium from 2000.

It is inevitable that legacy BIOS will be removed in a future release. To ease this transition as best we can, there will be a period (of at least one Fedora release) where it will be possible to boot using the legacy BIOS codepaths, but new installations will not be possible. While it would be easier for us to cut support off today, our hope is that this compromise position will make for a smoother transition. Additional support with issues during the transition would be appreciated.

While this will eventually reduce workload for boot/installation components (grub2 reduces surface area, syslinux goes away entirely, anaconda reduces surface area), the reduction in support burden extends much further into the stack - for instance, VESA support can be removed from the distro.

Fedora already requires a 2GHz dual core CPU at minimum (and therefore mandates that machines must have been made after 2006). Like the already accepted Fedora 37 change to retire ARMv7 support, the hardware targeted tends to be rather underpowered by today’s standards, and the world has moved on from it. Intel stopped shipping the last vestiges of BIOS support in 2020 (as have other vendors, and Apple and Microsoft), so this is clearly the way things are heading - and therefore aligns with Fedora’s “First” objective.

Feedback

Dropping legacy BIOS was previously discussed (but not proposed) in 2020: https://lists.fedoraproject.org/archives/list/devel%40lists.fedoraproject.org/thread/QBANCA2UAJ5ZSMDVVARLIYAJE66TYTCD/

Important, relevant points from that thread (yes, I reread the entire thread) that have informed this change:

  • Some machines are BIOS-only. This change does not prevent their use yet, but they are effectively deprecated. grub2 (our default bootloader) is already capable of both BIOS and UEFI booting.
  • Drawing a clear year cutoff, let alone a detailed list of hardware this change affects, is basically impossible. This is unfortunate but unlikely to ever change.
  • There is no migration story from Legacy BIOS to UEFI - repartitioning effectively mandates a reinstall. As a result, we don’t drop support for existing Legacy BIOS systems yet, just new installations.
  • There is no way to deprecate hardware without causing some amount of friction.
  • While at the time AWS did not support UEFI booting, that is no longer the case and they support UEFI today.

During mailing list discussion of this change, concern was expressed that some of the smaller hosting providers who do not provision with UEFI today and do not also support Windows would drop Fedora rather than enabling UEFI. Given that the major virtualization solutions (vsphere, kvm, xen, bhve, virtualbox, ...) all support UEFI today, this would likely be exposing an existing capability rather than making a sweeping change. That said, it is always possible that providers may elect to drop Fedora rather than adjust their setups - be it for this change or any other change Fedora makes.

There are also a nonzero number of Fedora users running otherwise-capable machines that appear to be legacy-only. While this change does not prevent their use, opposition has been voiced toward preventing reinstalls and more generally deprecating them at all.

Benefit to Fedora

UEFI is required for many desirable features, including applying firmware updates (fwupd) and supporting SecureBoot. As a standalone change, it reduces support burden on everything involved in installing Fedora, since there becomes only one way to do it per platform. Finally, it simplifies our install/live media, since it too only has to boot one way per arch. Freedom Friends Features First - this is that last one.

Scope

  • Proposal owners:
    • bootloaders: No change (existing Legacy BIOS installations still supported).
    • anaconda: No change (there could be only optional cleanups in the code). However, it needs to be verified.
    • Lorax: Code has already been written: https://github.com/weldr/lorax/pull/1205
  • 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

Systems currently using Legacy BIOS for booting on x86_64 will continue to do so.

However, this modifies the baseline Fedora requirements and some hardware will no longer be supported for new installations.

How To Test

UEFI installation has been supported for quite a while already, so additional testing there should not be required.

User Experience

Installs will continue to work on UEFI, and will not work on Legacy BIOS. Our install media is already UEFI-capable.

Dependencies

None

Contingency Plan

Leave things as they are. Code continues to rot. Community assistance is required to continue the status quo. Current owners plan to orphan some packages regardless of whether the proposal is accepted.

Another fallback option could be, if a Legacy BIOS SIG organizes, to donate the relevant packages there and provide some initial mentoring. Longer term, packages that cannot be wholly donated could be split, though it is unclear whether the synchronization thereby required would reduce the work for anyone.

  • Contingency mechanism: Delay until next release.
  • Contingency deadline: Beta freeze
  • Blocks release? No

Documentation

See release notes.

Release Notes

Fedora 37 marks legacy BIOS installation as deprecated on x86_64 in favor of UEFI. While systems already using Legacy BIOS to boot are still supported, new legacy BIOS installations on these architectures are no longer possible. Legacy BIOS support will be removed entirely in a future Fedora.

(Additionally, the Hardware Overview page should be updated to mention the UEFI requirement.)

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