Hacker News Reader

Would it be possible to define a "zone" that GRUB_SAVEDEFAULT can overwrite?

I reverted from btrfs to ext4 on my main desktop a few years ago, because grub couldn't remember the last selected menu item (error: sparse file not allowed), and I didn't feel like creating a dedicated /boot partition.

View on HN

Booting from zoned device on btrfs is not supported, the 0th zone contains the super block and the boot loader data are before any superblock so updating them would require reset and complete rewrite of the live data in the zone.

The 'sparse file file not found' is caused by grub, it would try to overwrite file blocks directly, but on btrfs it would cause checksum mismatch. This has been solved by storing the env block outside of the filesystem at 256K and synced back and forth once the system is booted. 256K is ok as btrfs does not use the first 1M on any device for bootloaders.

Reply on news.ycombinator.com