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. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)chroot.2 8.1 (Berkeley) 6/4/93 33.\" $FreeBSD: src/lib/libc/sys/chroot.2,v 1.7.2.8 2002/12/11 14:06:37 ru Exp $ 34.\" 35.Dd August 1, 2010 36.Dt CHROOT 2 37.Os 38.Sh NAME 39.Nm chroot 40.Nd change root directory 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.In unistd.h 45.Ft int 46.Fn chroot "const char *dirname" 47.Ft int 48.Fn chroot_kernel "const char *dirname" 49.Sh DESCRIPTION 50.Fa Dirname 51is the address of the pathname of a directory, terminated by an ASCII NUL. 52.Fn Chroot 53causes 54.Fa dirname 55to become the root directory, 56that is, the starting point for path searches of pathnames 57beginning with 58.Ql / . 59.Pp 60In order for a directory to become the root directory 61a process must have execute (search) access for that directory. 62.Pp 63It should be noted that 64.Fn chroot 65has no effect on the process's current directory. 66.Pp 67This call is restricted to the super-user. 68.Pp 69Depending on the setting of the 70.Va kern.chroot_allow_open_directories 71sysctl variable, open filedescriptors which reference directories 72will make the 73.Fn chroot 74fail as follows: 75.Pp 76If 77.Va kern.chroot_allow_open_directories 78is set to zero, 79.Fn chroot 80will always fail with 81.Er EPERM 82if there are any directories open. 83.Pp 84If 85.Va kern.chroot_allow_open_directories 86is set to one (the default), 87.Fn chroot 88will fail with 89.Er EPERM 90if there are any directories open and the 91process is already subject to a 92.Fn chroot 93call. 94.Pp 95Any other value for 96.Va kern.chroot_allow_open_directories 97will bypass the check for open directories 98.Pp 99Upon successful completion, a value of 0 is returned. Otherwise, 100a value of -1 is returned and 101.Va errno 102is set to indicate an error. 103.Pp 104The 105.Fn chroot_kernel 106system call adjusts the kernel's internal namecache and root vnode 107references to 108.Fa dirname . 109If used in conjunction with 110.Fn chroot 111during early boot, it allows for changing the root mount to any 112mount point available at that time. 113.Sh ERRORS 114.Fn Chroot 115will fail and the root directory will be unchanged if: 116.Bl -tag -width Er 117.It Bq Er ENOTDIR 118A component of the path name is not a directory. 119.It Bq Er EPERM 120The effective user ID is not the super-user, or one or more 121filedescriptors are open directories. 122.It Bq Er ENAMETOOLONG 123A component of a pathname exceeded 255 characters, 124or an entire path name exceeded 1023 characters. 125.It Bq Er ENOENT 126The named directory does not exist. 127.It Bq Er EACCES 128Search permission is denied for any component of the path name. 129.It Bq Er ELOOP 130Too many symbolic links were encountered in translating the pathname. 131.It Bq Er EFAULT 132.Fa dirname 133points outside the process's allocated address space. 134.It Bq Er EIO 135An I/O error occurred while reading from or writing to the file system. 136.El 137.Sh SEE ALSO 138.Xr chdir 2 , 139.Xr jail 2 140.Sh HISTORY 141The 142.Fn chroot 143function call appeared in 144.Bx 4.2 . 145