Poul-Henning Kamp says, in this discussion, we will review existing systems that provide strong separation via access control, virtualization, namespace management, and partitioning. We will then explore the FreeBSD Jail system, implemented by us, which adopts a hybrid approach to applying security primitives. We will pay particular attention to the implementation and administrative costs of modifying an existing system. We will also make recommendations for the design of new systems to facilitate the future introduction of security and separation features. These recommendations will reach the somewhat unsurprising conclusion that the path to security turns out to also be the path of improved and intentional software design and abstraction. Read more.