Based on the book "FreeBSD Mastery: Jails" Jails started as a limited virtualization system, but over the last two years they've become more and more powerful. This talk takes you through what modern jails can do, discarding the limits of what they were and demonstrating what they can be today. Jails started as a limited virtualization system, but over the last two years they've become more and more powerful. This talk takes you through what modern jails can do, discarding the limits of what they were and demonstrating what they can be today. We'll cover jails using the base system and the new iocage toolkit, discussing: jails as VMs configuring the jail host properties and parameters jail management packages and upgrades base jails virtual networking with VNET firewalls in jails jails in jails resource restrictions You'll leave with an understanding of what modern jails can and cannot do, and hints for future development.