1.\" Copyright (c) 1983, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)chroot.2 8.1 (Berkeley) 6/4/93 29.\" $FreeBSD: src/lib/libc/sys/chroot.2,v 1.7.2.8 2002/12/11 14:06:37 ru Exp $ 30.\" 31.Dd August 1, 2010 32.Dt CHROOT 2 33.Os 34.Sh NAME 35.Nm chroot , 36.Nm chroot_kernel 37.Nd change root directory 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In unistd.h 42.Ft int 43.Fn chroot "const char *dirname" 44.Ft int 45.Fn chroot_kernel "const char *dirname" 46.Sh DESCRIPTION 47.Fa Dirname 48is the address of the pathname of a directory, terminated by an ASCII NUL. 49.Fn Chroot 50causes 51.Fa dirname 52to become the root directory, 53that is, the starting point for path searches of pathnames 54beginning with 55.Ql / . 56.Pp 57In order for a directory to become the root directory 58a process must have execute (search) access for that directory. 59.Pp 60It should be noted that 61.Fn chroot 62has no effect on the process's current directory. 63.Pp 64This call is restricted to the super-user. 65.Pp 66Depending on the setting of the 67.Va kern.chroot_allow_open_directories 68sysctl variable, open filedescriptors which reference directories 69will make the 70.Fn chroot 71fail as follows: 72.Pp 73If 74.Va kern.chroot_allow_open_directories 75is set to zero, 76.Fn chroot 77will always fail with 78.Er EPERM 79if there are any directories open. 80.Pp 81If 82.Va kern.chroot_allow_open_directories 83is set to one (the default), 84.Fn chroot 85will fail with 86.Er EPERM 87if there are any directories open and the 88process is already subject to a 89.Fn chroot 90call. 91.Pp 92Any other value for 93.Va kern.chroot_allow_open_directories 94will bypass the check for open directories 95.Pp 96Upon successful completion, a value of 0 is returned. Otherwise, 97a value of -1 is returned and 98.Va errno 99is set to indicate an error. 100.Pp 101The 102.Fn chroot_kernel 103system call adjusts the kernel's internal namecache and root vnode 104references to 105.Fa dirname . 106If used in conjunction with 107.Fn chroot 108during early boot, it allows for changing the root mount to any 109mount point available at that time. 110.Sh ERRORS 111.Fn Chroot 112will fail and the root directory will be unchanged if: 113.Bl -tag -width Er 114.It Bq Er ENOTDIR 115A component of the path name is not a directory. 116.It Bq Er EPERM 117The effective user ID is not the super-user, or one or more 118filedescriptors are open directories. 119.It Bq Er ENAMETOOLONG 120A component of a pathname exceeded 255 characters, 121or an entire path name exceeded 1023 characters. 122.It Bq Er ENOENT 123The named directory does not exist. 124.It Bq Er EACCES 125Search permission is denied for any component of the path name. 126.It Bq Er ELOOP 127Too many symbolic links were encountered in translating the pathname. 128.It Bq Er EFAULT 129.Fa dirname 130points outside the process's allocated address space. 131.It Bq Er EIO 132An I/O error occurred while reading from or writing to the file system. 133.El 134.Sh SEE ALSO 135.Xr chdir 2 , 136.Xr jail 2 137.Sh HISTORY 138The 139.Fn chroot 140function call appeared in 141.Bx 4.2 . 142