GRUB (GRand Unified Bootloader): Recent Developments and Future Directions

The GRUB project, a cornerstone of Linux bootloaders, continues its evolution, incorporating new features, enhanced security, and performance optimizations. This overview summarizes key updates based on the FOSDEM 2025 presentation by Daniel Kiper, a GRUB upstream maintainer at Oracle, delivered in Brussels on February 1st, 2025.

Table of Contents

• Key GRUB Enhancements
  • 1. Past Year's Achievements
  • 2. Current Development Focus
• Fedora's Contributions
• The Future of GRUB

What is GRUB?

GRUB (GRand Unified Bootloader) is a versatile bootloader powering most Linux distributions. Its primary function is initiating the operating system at startup. GRUB provides users with the ability to select from multiple operating systems, adjust boot settings, and manage system recovery options.

Key GRUB Enhancements

1. Past Year's Achievements

Significant advancements in GRUB over the past year include:

• EROFS Integration: Enhanced Read-Only File System (EROFS) support is now integrated, boosting performance and storage efficiency for read-only partitions.
• Strengthened Security: Building GRUB with --disable-cli disables command-line access and menu editing, mitigating potential security risks.
• Enhanced EFI Security: Core NX (Non-Executable) bit support on EFI platforms improves memory protection.
• Improved PE File Handling: Stricter alignment with page size (minimum 4KB) ensures compatibility with modern hardware and security standards.
• Robust Memory Protection: GRUB now prevents sections from being simultaneously writable and executable, a crucial security enhancement.
• Secure Boot Improvements: SBAT (Secure Boot Attribute Table) support for ELF files and Appended Signature Secure Boot for PowerPC systems strengthen system integrity.
• TPM2-Based Disk Unlocking: Seamless disk unlocking using TPM2 is now available for EFI and IEEE1275 PowerPC platforms.
• Advanced Font Handling: The build system features improved font detection for better user interface rendering.
• Streamlined Patch Management: Increased integration of downstream patches into the main GRUB codebase reduces fragmentation.

2. Current Development Focus

The GRUB team is actively pursuing several key improvements:

1. Shim Loader Protocol Support (EFI): Enhanced compatibility with secure boot implementations.
2. TrenchBoot Integration (x86): Integration of TrenchBoot, a boot process security project, for both Intel and AMD systems.
3. BLS and UKI Support: Adding Boot Loader Specification (BLS) and Unified Kernel Image (UKI) support to optimize boot processes.
4. Library Modernization: Updating embedded libraries, including libgcrypt (for Argon2 KDF), to the latest versions.
5. Continuous Integration: Development of a CI (Continuous Integration) system to automate testing and improve code quality.
6. Upcoming Release: A code freeze and subsequent GRUB release are planned in the near future.

Fedora's Contributions

Alec Brown from Oracle presented data on Fedora's downstream GRUB patches:

• GRUB 2.02: Across 11 Fedora versions (21-31), patch numbers increased from 151 to 370, reflecting both backported and new contributions.
• GRUB 2.04: Fedora 32 and 33 saw a total of 437 patches (28 backported, 67 new).
• GRUB 2.06: Fedora 34-40 saw a further increase to 544 patches (84 backported, 98 new).

This demonstrates the strong collaborative relationship between the GRUB upstream team and Fedora, with a growing trend of Fedora patches being integrated into the main codebase.

The Future of GRUB

GRUB's ongoing development ensures its position as a leading Linux bootloader. Future efforts will focus on:

• Continued upstream integration of Fedora patches.
• Enhanced security, particularly for Secure Boot and TPM-based authentication.
• Improvements to the testing framework for reliability on modern hardware.

For comprehensive details, please refer to the full presentation.

Further Reading:

• How To Configure GRUB2 Boot Loader Settings In Ubuntu
• How To Password Protect GRUB Bootloader In Linux
• How To Change GRUB Theme In Linux

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