Jails (on FreeBSD) each get their own IP address(es) which may be associated with the same network interface. With ZFS, one can use a common "template" filesys

Jails (on FreeBSD) each get their own IP address(es) which may be associated with the same network interface. With ZFS, one can use a common "template" filesystem for jails such that updates to the userland or the ports tree only need to be applied to the base file system once and become visible in all jails (as far as I understand ZFS, at least). To my knowledge, it is not possible to have a process be visible in several jails at once. Each process has a jail ID associated with it, and it is visible only inside the corresponding jail (and the host system, of course).