diskless mode: boot device can not be unmounted (Resource busy)
Attempting to unmount the boot device of "diskless" systems, e.g. the stock iso9660 installation images but also ext4 partitions, results in "Resource busy" errors.
Unmounting the boot device becomes possible after an
umount /dev/loop0, but this breaks the "diskless" system (as /lib/modules is gone).
Seems like the modloop is not (re?)loaded and detached to reside purely in (z)ram, or something, so that it actually ends up working independent from the boot device.