busybox initramfs loop mount

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http://unix.stackexchange.com – I'm trying to loop mount my root filesystem (a loop file) within a busybox initramfs. I try to run the command: mount /rootfs.raw /root ... which works on my Ubuntu laptop, however, I simply get mount: mounting /dev/loop0 on /root failed: Invalid argument No matter what combination of options I use, (including loading to /loop0 manually and trying to mount it), the system will not mount the loop device. Why can't I mount it? (HowTos)