Fedora Cloud Looks to Switch /Boot to Btrfs Subvolume

With Fedora 43 releasing in the coming weeks, Fedora stakeholders are beginning to plot their feature ideas for next year's Fedora 44 release. One of the early F44 feature submissions pending approval is switching /boot on Fedora Cloud images to being a Btrfs file-system subvolume.

Fedora Cloud for cloud platforms and Vagrant is looking to drop a separate /boot partition in favor of using a Btrfs subvolume in the main Btrfs operating system volume. In turn this should provide better space utilization and smaller cloud images.

Though due to platform limitations this /boot Btrfs subvolume doesn't apply to UEFI-UKI and s390x cloud images. Besides encountering platform limitations for handling Btrfs /boot, preventing this approach from being used elsewhere is also a known bug with GRUB being unable to use the bootloader header space for grubenv on Btrfs. But a patch is pending there.

"Fedora Cloud Edition is typically deployed as images of fixed sizes and grown on deployment, so it is attractive for us to minimize the footprint of the image up-front. Since Fedora Cloud images do not rely on grubenv features like the GRUB Hidden Menu feature (which requires resolving rhbz#2372973 first), we can easily consolidate the bootloader data on the Btrfs volume. By using a Btrfs subvolume, it can be trivially omitted from any snapshot mechanisms used on the deployment while avoiding space contention for boot data and the rest of the operating environment data."

Those wanting to learn more about the proposed Btrfs boot for Fedora Cloud images can see this change proposal that will be evaluated soon by the Fedora Engineering and Steering Committee.