A use case I did not plan for smolBSD, start it with 9p directory sharing in order to access a NetBSD raw disk image:
$ /startnb.sh -i images/base-amd64.img -k kernels/netbsd-SMOL -w /mnt/nfs
# vnconfig vnd0 /mnt/vm/nadd/disk0.img
# mount /dev/vnd0e /somewhere
happily crawl your old disk backup