You will need to load the kernel module 'fuse' to use this package. To load
this at boot time, add the following line to /boot/loader.conf:

fuse_load="YES"

If you want unprivileged users to be able to use unionfs, add the following
line to /etc/sysctl.conf:

vfs.usermount=1

You can enable them immediately with:

kldload fuse
sysctl vfs.usermount=1