Beatm is used to manage boot environments. That can help you to rollback an upgrade in case it makes problems.

To install it:

/usr/ports/sysutils/beadm
make install
make clean

We have an already existing standard ZFS folder structure. To get this working with boot environments we have to modify it a little bit.

At first we install beadm:

portsnap fetch
portsnap extract
cd /usr/ports/sysutils/beadm
make install clean

Now we clone our existing system and convert it to beadm aware structure:

zfs create -o mountpoint=none zroot/ROOT 
zfs snapshot zroot@be 
zfs clone zroot@be zroot/ROOT/default
zpool set bootfs=zroot/ROOT/default zroot
reboot (before executing this, make sure you are on FreeBSD 9.2 and to pool to boot is not defined in /boot/loader.conf)

Now we can run the beadm tool.

To finish it now, we remove the old structure:

zfs promote zroot/ROOT/default
mkdir /mnt/test
zfs set mountpoint=/mnt/test zroot
cd /mnt/test
chflags -R noschg *
rm -R *
rm -R .*
cd ..
zfs set mountpoint=none zroot

beadm list 
beadm activate default 
reboot