FreeBSD ZFS datasets can be jailed, which removes them from the hosts visibility but allows them to be seen by a jail they are assigned to.
The first step of giving a jail access to a ZFS filesystem is to enable the jailed property.
zfs create zroot/my-jail-dataset
zfs set jailed=on zroot/my-jail-dataset
After this preparation iocage may automatically assign it to the jail on launch.
ioc set jail_zfs_dataset=zroot/my-jail-dataset my-jail
Note: Like other Jail Config list properties, multiple datasets can be specified comma separated.
Doing the same in Python requires to set a list structure containing the target jails datasets
import ioc
jail = ioc.Jail("my-jail")
jail.config["jail_zfs_dataset"] = ["zroot/my-jail-dataset"]
jail.save()
Because of the jailed=on ZFS dataset property the dataset is not returned to the host after the jail was stopped.
It is not possible to assign a dataset to multiple jails.