In setting up filesystem images for USB disks, I'd like the ability to
install GRUB to a disk image, rather than directly to a USB disk.
Specifically, I'd like to point it at a disk image and a separate
directory to put /boot/grub in, as grub-install appears to allow.
However, grub-install always tries to probe for the device containing
the image file rather than just using the image file (no, I *don't* want
it to touch my root filesystem's device, thank you; fortunately I ran it
as non-root), and grub-setup only supports passing a parenthesized GRUB
device name.
I don't mind having to manually specify the filesystem module rather
than having GRUB detect which one it needs. I also don't mind
specifying some of the things grub-setup detects, such as whether it
will boot from a hard disk and need the BIOS disk numbering workaround
(it will).
Right now, my build process for a USB disk image involves having a real
USB disk plugged in during the build, an annoying requirement.
- Josh Triplett