# gpart delete -i 4 /dev/ada0s1
ada0s1d deleted
# gpart delete -i 5 /dev/ada0s1
ada0s1e deleted
# gpart add -s 2G -t freebsd-ufs /dev/ada0s1
ada0s1d added
# mkdir /mnt/ufs_root
# mount /dev/ada0s1a /mnt/bootdir
# zpool import -R /mnt/vault vault
# mount -t zfs vault/root /mnt/oldroot/
# newfs -m 0 /dev/ada0s1d
# mount /dev/ada0s1d /mnt/ufs_root
# cp -Rp /mnt/oldroot/ /mnt/ufs_root/
# cat /mnt/ufs_root/etc/rc.conf 
zfs_enable="YES"
hostname="tara"
ifconfig_nfe0="inet 10.0.0.2 netmask 255.255.255.0"
sshd_enable="yes"
dumpdev="AUTO"
istgt_enable="YES"
powerd_enable="YES"
tftpd_enable="YES"
tftpd_flags="-p -s /usr/tftpboot -B 1024 --ipv4"
inetd_enable="YES"
fsck_y_enable="YES"
background_fsck="NO"
mountd_enable="YES"
rpcbind_enable="YES"
nfs_server_enable="YES"
samba_enable="YES"
samba_config="/usr/local/etc/samba/smb.conf"
defaultrouter="10.0.0.1"
# vi /mnt/bootdir/boot/loader.conf
# cat /mnt/bootdir/boot/loader.conf
zfs_enable="YES"
zfs_load="YES"
vfs.root.mountfrom="ufs:/dev/ada0s1d"
autoboot_delay="1"
# umount /mnt/oldroot
# zfs umount -a
# umount /mnt/ufs_root
# umount /mnt/bootdir
# reboot