To facilitate better understanding of parts of the FreeBSD system related to jails, their internals and the way they interact with the rest of FreeBSD, the following terms are used further in this chapter:
Utility, which uses chroot(2) FreeBSD system call to change the root directory of a process and all its descendants.
The environment of processes running in a “chroot”. This includes resources such as the part of the file system which is visible, user and group IDs which are available, network interfaces and other IPC mechanisms, etc.
The system administration utility which allows launching of processes within a jail environment.
The controlling system of a jail environment. The host system has access to all the hardware resources available, and can control processes both outside of and inside a jail environment. One of the important differences of the host system from a jail is that the limitations which apply to superuser processes inside a jail are not enforced for processes of the host system.
A process, user or other entity, whose access to resources is restricted by a FreeBSD jail.