1.\" $NetBSD: chroot.2,v 1.15 2002/02/08 01:28:16 ross Exp $ 2.\" 3.\" Copyright (c) 1983, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)chroot.2 8.1 (Berkeley) 6/4/93 35.\" 36.Dd April 18, 2001 37.Dt CHROOT 2 38.Os 39.Sh NAME 40.Nm chroot 41.Nd change root directory 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.Fd #include \*[Lt]unistd.h\*[Gt] 46.Ft int 47.Fn chroot "const char *dirname" 48.Ft int 49.Fn fchroot "int fd" 50.Sh DESCRIPTION 51.Fa dirname 52is the address of the pathname of a directory, terminated by an ASCII NUL. 53.Fn chroot 54causes 55.Fa dirname 56to become the root directory, 57that is, the starting point for path searches of pathnames 58beginning with 59.Ql / . 60.Pp 61In order for a directory to become the root directory 62a process must have execute (search) access for that directory. 63.Pp 64If the current working directory is not at or under the new root 65directory, it is silently set to the new root directory. 66It should be noted that, on most other systems, 67.Fn chroot 68has no effect on the process's current directory. 69.Pp 70This call is restricted to the super-user. 71.Pp 72The 73.Fn fchroot 74function performs the same operation on an open directory file 75known by the file descriptor 76.Fa fd . 77.Sh RETURN VALUES 78Upon successful completion, a value of 0 is returned. Otherwise, 79a value of -1 is returned and 80.Va errno 81is set to indicate an error. 82.Sh ERRORS 83.Fn chroot 84will fail and the root directory will be unchanged if: 85.Bl -tag -width Er 86.It Bq Er ENOTDIR 87A component of the path name is not a directory. 88.It Bq Er ENAMETOOLONG 89A component of a pathname exceeded 90.Dv {NAME_MAX} 91characters, or an entire path name exceeded 92.Dv {PATH_MAX} 93characters. 94.It Bq Er ENOENT 95The named directory does not exist. 96.It Bq Er EACCES 97Search permission is denied for any component of the path name. 98.It Bq Er ELOOP 99Too many symbolic links were encountered in translating the pathname. 100.It Bq Er EFAULT 101.Fa dirname 102points outside the process's allocated address space. 103.It Bq Er EIO 104An I/O error occurred while reading from or writing to the file system. 105.El 106.Pp 107.Fn fchroot 108will fail and the root directory will be unchanged if: 109.Bl -tag -width Er 110.It Bq Er EACCES 111Search permission is denied for the directory referenced 112by the file descriptor. 113.It Bq Er EBADF 114The argument 115.Fa fd 116is not a valid file descriptor. 117.It Bq Er EIO 118An I/O error occurred while reading from or writing to the file system. 119.It Bq Er ENOTDIR 120The argument 121.Fa fd 122does not reference a directory. 123.El 124.Sh SEE ALSO 125.Xr chdir 2 126.Sh HISTORY 127The 128.Fn chroot 129function call appeared in 130.Bx 4.2 . 131Working directory handling was changed in 132.Nx 1.4 133to prevent one way a process could use a second 134.Fn chroot 135call to a different directory to "escape" from the restricted subtree. 136The 137.Fn fchroot 138function appeared in 139.Nx 1.4 . 140