Bug#1102160: upgrade-reports: Bookworm to Trixie [amd64][EFI] initramfs unpacking failed invalid magic at start of compressed archive

[Felix Zielcke]

Am Freitag, dem 18.04.2025 um 19:10 +0300 schrieb Martin-Éric Racine:
> The Debian changelog suggests what caused this:
> 
> Someone enabled compiling GRUB with FUSE3 to enhance QEMU support.
> The problem with FUSE3 is that it only has very basic support for
> btrfs, lacking among other things support for subvolumes. This is a
> serious issue considering how widely spread btrfs has become and how
> debian-installer uses subvolumes by default whenever someone selects
> brtfs as the filesystem type. Rendering hosts unbootable is a big
> no-no. I would really hope the release team to step in on this one.
> 
> Martin-Éric
> 

Hi Martin-Éric,

FUSE support in GRUB 2 is only used for the grub-mount binary. And not
at all in the actual booting code loaded from EFI/BIOS.

You could though test the fs drivers of it with grub-mount:

grub-mount /dev/sda2 /mnt (replace sda2 with your / partition)
sha1sum /mnt/@rootfs/boot/initrd.img-6.12.20-amd64
sha1sum /@rootfs/boot/initrd.img-6.12.20-amd64

both commands should output the same hash sum.
And yes, this is safe with a mounted fs because the GRUB fs code is
100% complete read-only.

Felix