Fedora approves a smaller GRUB [LWN.net]
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Fedora approves a smaller GRUB
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By Joe Brockmeier<br>July 29, 2026
Leo Sandoval and Marta Lewandowska have put forward a change<br>proposal for Fedora 45, which is expected in October, to<br>provide a separate, slimmed-down version of GRUB for a niche use<br>case. The new package would be in addition to the main GRUB package<br>and would not replace it for the majority of Fedora users. The idea<br>met with some resistance from Fedora contributors who thought that it<br>would be better to use systemd-boot,<br>or another modern bootloader, rather than trying to wrangle GRUB into<br>a suitable state for the use case. The Fedora Engineering Steering<br>Council (FESCo), however, voted<br>to accept the change on July 7.
Signed, sealed, booted
The change proposal specifies the creation of a UEFI-only build of<br>GRUB with a minimal set of modules for booting unified<br>kernel images (UKIs) using boot<br>loader specification (BLS) files. The target use case is for<br>booting "sealed<br>bootable container" images in virtual environments (e.g., running<br>virtual machines in public clouds) for confidential<br>computing.
LWN has covered bootable<br>containers (bootc) in the past, but sealed bootc images are relatively<br>new. A sealed image is one with all of the components for a fully<br>verified boot chain: that includes firmware, the UKI, and a composefs<br>repository, with fs-verity enabled, for the<br>filesystem rather than OSTree, which has<br>traditionally been used for bootc. A sealed image relies on Secure<br>Boot and currently is only supported on x86_64 and aarch64 systems<br>with UEFI.
The main users of the new GRUB package, according to the<br>proposal, will be the Fedora<br>CoreOS developers. Since CoreOS is meant to be a minimal, automatically<br>updated operating system, the hope is that a stripped-down GRUB with fewer<br>built-in modules will have a smaller attack surface and require less-frequent<br>updates. CoreOS may be the first user of the new GRUB build, but the proposal<br>envisions "a minimal UEFI bootloader for virtual environments that can be<br>further tailored for use in those environments".
It is interesting to see Lewandowska, who is a Red Hat quality engineer, now<br>endorsing GRUB for this use case after arguing that it should be replaced not long<br>ago. She gave a a talk at<br>DevConf.cz, in 2024, about a project called nmbl (for<br>"no more bootloader", pronounced "nimble") that would replace GRUB for use with<br>UKIs. Instead of using a separate bootloader, nmbl would use the Linux kernel as<br>its own bootloader. Her blog<br>post that was published to coincide with the talk gives a good overview of<br>nmbl, as well as its anticipated advantages over GRUB.
She pointed out at the time that Red Hat was carrying "hundreds<br>of downstream patches" for the project and had argued that GRUB<br>was too complex. Lewandowska also pointed out the large<br>number of vulnerabilities it had been subject to over time, as<br>well as all of the filesystem, storage, and memory-allocation bugs<br>that she said GRUB's developers did not have the time to fix.
During the proposal discussion,<br>Lewandowska explained<br>her change of heart regarding GRUB, at least in part: "This year GRUB<br>upstream moved to GitLab, has much better [continuous integration], become more<br>accessible and much more lively." It would appear that work on nmbl has<br>stalled as GRUB has had a revival: the<br>repository that seems to have the most up-to-date work on the project, a dracut plugin for working with<br>nmbl, was last updated in August 2025. The proposal does not mention nmbl at<br>all.
Why not systemd-boot?
The original vision for sealed bootable containers called for using<br>systemd-boot rather than GRUB. The proposal mentions that systemd-boot was considered,<br>but was rejected for several reasons. It argued that systemd-boot<br>"has not been widely tested or fuzzed, like GRUB has been", and<br>that long-term maintenance of more than one bootloader would add<br>technical debt. An early<br>version of the proposal claimed that the systemd team would<br>"view any additional features [for systemd-boot] as a<br>no-go".
Fedora change discussions are still conducted on both its discussion forum<br>and the Fedora development mailing list, though a<br>proposal to change that and move discussions solely to the mailing list is<br>currently being entertained. This meant that the discussion was, naturally, a<br>bit fragmented. On the forum, Zbigniew Jędrzejewski-Szmek said<br>that the arguments against systemd-boot...