gpt
===

truncate -s 1G freebsd.img
mdconfig -f freebsd.img
gpart create -s gpt md0
gpart add -t freebsd-boot -l gpboot -s 512K md0
gpart bootcode -b /boot/pmbr -p /boot/gptboot -i 1 md0
gpart add -t freebsd-ufs -l gprootfs -b 1M md0
newfs /dev/gpt/gprootfs
mount /dev/gpt/gprootfs /mnt2

setenv DESTDIR /mnt2
make installworld installkernel distribution

etc/fstab:

 # Device        Mountpoint      FStype  Options Dump    Pass#
 /dev/gpt/gprootfs   /           ufs     rw      1       1

 etc/ttys for bhyve, use unit 2 for PCI device:
#ttyu2  "/usr/libexec/getty std.9600"   dialup  off secure
ttyu2   "/usr/libexec/getty std.9600"   vt100   on  secure

umount /mnt2
mdconfig -d -u 0


mbr
===

gpart create -s mbr  /dev/da0
gpart add -b 63 -s 1G -t freebsd da0   # adds da0s1

gpart create -s bsd da0s1
gpart add -i 1 -b 16 -s 800M -t freebsd-ufs da0s1 # could be larger 

gpart bootcode -b /boot/mbr da0
gpart bootcode -b /boot/boot da0s1

newfs /dev/da0s1a
mount /dev/da0s1a /mnt
make installworld installkernel distribution

vi /mnt/etc/fstab
 # Device        Mountpoint      FStype  Options Dump    Pass#
 /dev/da0s1a     /               ufs     rw      1       1