dd if=/dev/zero of="${rootfs}" count=${size_mb} bs=1M \
|| cleanup tmpmnt
-mkfs.${fs} -L lunaix-rootfs -r 0 "${rootfs}" \
+${prefix} mkfs.${fs} -L lunaix-rootfs -r 0 "${rootfs}" \
|| cleanup tmpmnt img
${prefix} mount -o loop "${rootfs}" "${tmp_mnt}" \