When I submitted PR I missed adding support for partitions and slices. To reproduce: $ sudo mdconfig ~/FreeBSD-14.0-RELEASE-arm64-aarch64-RPI.img md0 $ sudo umount -d /mnt umount: invalid md device: /dev/md0s2a Fix: https://github.com/freebsd/freebsd-src/pull/1183
Fix was merged.