Comment 9 for bug 1876258

Curtin is collecting by-id links to disk to populate grub2 's debconf value:

grub-pc grub-pc/install_devices

It's not clear to me (yet) if providing non persistent values (like /dev/sda) will work with

/usr/lib/grub/grub-multi-install

Even if it accepts non-by-id values; it's possible that on subsequent boots (with additional disks present) that /dev/sda might not point to the disk that has grub.

So we can change this from an error by falling back on the path value, but it's just not safe. Disks need persistent attributes (like serial) for persistent links to work as expected.