Disallow UEFI on MBR for x86 in Anaconda
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
Enforce the use of GPT partition tables for all UEFI-based Fedora installations for x86 architecture. This removes support for installing Fedora in UEFI mode on MBR-partitioned disks on x86 systems. ARM and RISC-V remain unaffected.
Owner
- Name: Anaconda team (Katerina Koukiou)
- Email: kkoukiou@redhat.com
Current status
- Targeted release: Fedora Linux 43
- Last updated: 2025-07-03
- Announced
- Discussion thread
- 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
Anaconda will no longer support installing in UEFI mode on MBR-partitioned disks for X886. While the UEFI specification technically permits booting from MBR (msdos) disks, in practice this configuration is unreliable, inconsistently supported by firmware, and not tested in Fedora.
Fedora’s GRUB2 bootloader documentation already assumes the use of a GPT partition table for UEFI installations.
By enforcing GPT in UEFI mode, Anaconda will provide a more robust installation experience by avoiding bootloader crashes (e.g., efibootmgr failures).
Support for UEFI on MBR was originally added in blivet#764 to accommodate cloud image use cases, such as AWS, which at the time did not support UEFI booting on GPT disks. These constraints no longer apply to modern cloud platforms, making MBR-based UEFI setups unnecessary for current Fedora deployments.
This change only applies to x86 systems booted in UEFI mode. Other architectures (such as ARM and RISC-V) are not affected, as their UEFI implementations may still depend on MBR partitioning.
Feedback
Benefit to Fedora
- Improved reliability: Eliminating support for MBR in UEFI installations prevents bootloader failures caused by firmware or efibootmgr being unable to register UEFI boot entries on MBR disks.
- Reduced support burden: Dropping an untested and rarely used configuration makes Fedora easier to test and maintain. It also avoids misleading users into thinking MBR+UEFI is a viable long-term setup.
Scope
- Proposal owners: The upstream PR is ready
- Other developers:
- Release engineering: #Releng issue number
- Policies and guidelines: N/A (not needed for this Change)
- Trademark approval: N/A (not needed for this Change)
- Alignment with the Fedora Strategy:
Upgrade/compatibility impact
This change does not affect upgrades of existing Fedora systems, as it only impacts the Anaconda installation path in UEFI mode on MBR-partitioned disks. Systems that were previously installed with MBR and UEFI may continue to function and upgrade normally, but new installations via Anaconda will require GPT.
Early Testing (Optional)
Do you require 'QA Blueprint' support? Y/N
How To Test
After Anaconda PR #6484 is merged, users can test this change by downloading a current Fedora Rawhide ISO and attempting to install Fedora in UEFI mode on an MBR-partitioned disk on a x86 system.
The installer should fail gracefully with a clear error message indicating that GPT is required for UEFI installations.
User Experience
Dependencies
Contingency Plan
- Contingency mechanism: (What to do? Who will do it?) N/A (not a System Wide Change)
- Contingency deadline: N/A (not a System Wide Change)
- Blocks release? N/A (not a System Wide Change), Yes/No
Documentation
N/A (not a System Wide Change)
