chroot

chroot is a shell command and a system call on Unix and Unix-like operating systems that changes the apparent root directory for the current running process and its children. A program that is run in such a modified environment cannot name (and therefore normally cannot access) files outside the designated directory tree. The term chroot may refer to the system call or the command-line utility. The modified environment is called a chroot jail. thumb|Chroot: from Gentoo to Ubuntu