F37 proposal: Install Using GPT on x86_64 BIOS by Default (System-Wide Change proposal)

[Ben Cotton]

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

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 ==
This Change makes it so that Fedora Linux systems installed on legacy
x86 BIOS systems will get GPT partitioning by default instead of
legacy MBR partitioning. This makes x86 BIOS installs more similar to
x86 UEFI installs.

== Owner ==
* Name: [[User:Ngompa| Neal Gompa]], [[User:Dcavalca| Davide
Cavalca]], [[User:Salimma| Michel Alexandre Salim]],
[[User:Chrismurphy| Chris Murphy]]
* Email: ngompa13(a)gmail.com, dcavalca(a)fb.com, michel(a)michel-slm.name,
chrismurphy(a)fedoraproject.org


== Detailed Description ==
Once implemented, Anaconda will create a GPT disk table on
non-partitioned disks or when the disk is being completely reset when
Fedora x86 install/live media is booted in BIOS mode.


== Benefit to Fedora ==
This simplifies our default code path by using the same partitioning
scheme as UEFI systems and aligns us more to how Fedora variants that
are delivered as disk images, which all use a similar setup. It also
paves the way to implement hybrid BIOS+UEFI boot for legacy BIOS
installs to enable future conversion to UEFI boot or emulated UEFI
boot on legacy BIOS.

This is a step toward a longer transition to eventually eliminate
direct BIOS boot support, as identified in the discussion for
[[Changes/DeprecateLegacyBIOS|the rejected Change to deprecate BIOS
support in Fedora Linux 37]].

== Scope ==
* Proposal owners:
** Submit code changes to Anaconda to use GPT by default on BIOS
systems ([https://github.com/rhinstaller/anaconda/pull/4104
gh#rhinstaller/anaconda#4104])

* Other developers:
** Anaconda developers need to review and merge the pull request

* Release engineering: [https://pagure.io/releng/issue/10796 #10796]
* Policies and guidelines: N/A (not needed for this Change)
* Trademark approval: N/A (not needed for this Change)
* Alignment with Objectives: N/A (not needed for this Change)


== Upgrade/compatibility impact ==
There will be no impact for existing Fedora Linux systems that
upgrade. We will not convert the partitioning on upgrade. However,
some very old systems have buggy EFI implementations that do not
handle legacy BIOS boot on GPT well, and on those systems, users will
need to request Anaconda to create a legacy MBR partition table by
using <code>inst.mbr</code> on the boot command-line.


== How To Test ==
Currently, users can test by booting Fedora media on BIOS systems with
the <code>inst.gpt</code> option to try installing Fedora Linux on a
legacy BIOS boot system with a GPT disk. After the change is merged
and released, this behavior will be the default, and
<code>inst.mbr</code> would be required to go back to the previous
behavior.

== User Experience ==
In general, there should nothing materially changing for users. If
users look at the disk with <code>fdisk</code> or
<code>parted</code>,
they'll see a GPT disk instead of an MBR one and a BIOS boot partition
will be present, which stores the GRUB boot code on a GPT disk.

== Dependencies ==
This is isolated to Anaconda and is principally dependent on getting
the changes into Anaconda.


== Contingency Plan ==
* Contingency mechanism: Revert the change in upstream Anaconda
* Contingency deadline: Final Freeze
* Blocks release? Yes


== Documentation ==
The upstream documentation will be updated as part of the change in Anaconda.

== Release Notes ==
Fedora Linux now uses GPT (GUID Partition Table) partitioning by
default for x86_64 systems that use legacy BIOS instead of UEFI. This
brings a more modern method of partitioning disks and aligns closer
with UEFI-based installations, which already use GPT partitioning.


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