• modify /boot/loader.conf

geom_eli_load="YES"

• encrypt partition

# kldload geom_eli
# dd if=/dev/random of=/root/home.key bs=64 count=1
# geli init -s 4096 -K /root/home.key /dev/ada4p1
# geli attach -k /root/home.key /dev/ada4p1
# newfs -Uj /dev/ada4p1.eli

• modify /etc/rc.conf

geli_devices="ada4p1"
geli_ada4p1_flags="-k /root/home.key"

• modify /etc/fstab