The chroot utility was first implemented by Bill Joy in 1982. A chroot on the Unix operating system is an operation (system call/wrapper program) that changes the root directory for the current running process and its children. A process in such a modified environment cannot access files outside the designated directory tree. Chroot provides the guest OS / process with its own, segregated file system to run in, allowing applications to run in a binary environment different from the host OS. The modified environment is called chroot jail.