# truncate -s 1m /tmp/swapfile
# echo "md0.eli none swap sw,file=/tmp/swapfile 0 0" > /tmp/fstab
# /sbin/swapon -F /tmp/fstab -a
swapon: Bad device unit: md0.eli: Invalid argument
# /usr/obj/usr/src/arm64.aarch64/sbin/swapon/swapon -F /tmp/fstab -a
swapon: adding /dev/md0.eli as swap device
# swapinfo
Device 1K-blocks Used Avail Capacity
/dev/gpt/ssdswap0 8388608 0 8388608 0%
/dev/md0.eli 1024 0 1024 0%
Total 8389632 0 8389632 0%