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.\" $FreeBSD$ 34.\" 35.Dd June 4, 1993 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.Sh DESCRIPTION 48The 49.Fa dirname 50argument 51is the address of the pathname of a directory, terminated by an ASCII NUL. 52The 53.Fn chroot 54system call causes 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 64It should be noted that 65.Fn chroot 66has no effect on the process's current directory. 67.Pp 68This call is restricted to the super-user. 69.Pp 70Depending on the setting of the 71.Ql kern.chroot_allow_open_directories 72sysctl variable, open filedescriptors which reference directories 73will make the 74.Fn chroot 75fail as follows: 76.Pp 77If 78.Ql kern.chroot_allow_open_directories 79is set to zero, 80.Fn chroot 81will always fail with 82.Er EPERM 83if there are any directories open. 84.Pp 85If 86.Ql kern.chroot_allow_open_directories 87is set to one (the default), 88.Fn chroot 89will fail with 90.Er EPERM 91if there are any directories open and the 92process is already subject to the 93.Fn chroot 94system call. 95.Pp 96Any other value for 97.Ql kern.chroot_allow_open_directories 98will bypass the check for open directories 99.Pp 100Upon successful completion, a value of 0 is returned. Otherwise, 101a value of -1 is returned and 102.Va errno 103is set to indicate an error. 104.Sh ERRORS 105The 106.Fn chroot 107system call 108will fail and the root directory will be unchanged if: 109.Bl -tag -width Er 110.It Bq Er ENOTDIR 111A component of the path name is not a directory. 112.It Bq Er EPERM 113The effective user ID is not the super-user, or one or more 114filedescriptors are open directories. 115.It Bq Er ENAMETOOLONG 116A component of a pathname exceeded 255 characters, 117or an entire path name exceeded 1023 characters. 118.It Bq Er ENOENT 119The named directory does not exist. 120.It Bq Er EACCES 121Search permission is denied for any component of the path name. 122.It Bq Er ELOOP 123Too many symbolic links were encountered in translating the pathname. 124.It Bq Er EFAULT 125The 126.Fa dirname 127argument 128points outside the process's allocated address space. 129.It Bq Er EIO 130An I/O error occurred while reading from or writing to the file system. 131.El 132.Sh SEE ALSO 133.Xr chdir 2 , 134.Xr jail 2 135.Sh HISTORY 136The 137.Fn chroot 138system call appeared in 139.Bx 4.2 . 140.Sh BUGS 141If the process is able to change its working directory to the target 142directory, but another access control check fails (such as a check for 143open directories, or a MAC check), it is possible that this system 144call may return an error, with the working directory of the process 145left changed. 146