chroot —
change root directory
  
    | chroot | [ -Ggroup,group,...]
      [-ggroup]
      [-uuser]
      newroot [command] | 
The chroot command changes its root directory to the
  supplied directory newroot and exec's
  command, or, if not supplied, an interactive copy of
  your shell.
If the -u, -g, or
    -G options are given, the user, group, and group
    list of the process are set to these values after the chroot has taken
    place; see setgid(2),
    setgroups(2),
    setuid(2),
    getgrnam(3), and
    getpwnam(3).
Note: command or the shell are run as your
    real-user-id.
The following environment variable is referenced by
  chroot:
  - SHELL
- If set, the string specified by SHELLis
      interpreted as the name of the shell to exec. If the variableSHELLis not set, /bin/sh
      is used.
Thechroot utility first appeared in
  4.4BSD.
chroot should never be installed setuid root, as it
  would then be possible to exploit the program to gain root privileges.