CHROOT(2) BSD System Calls Manual CHROOT(2)NAMEchroot — change root directory
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <unistd.h>
int
chroot(const char *dirname);
int
fchroot(int fd);
DESCRIPTION
dirname is the address of the pathname of a directory, terminated by an
ASCII NUL. chroot() causes dirname to become the root directory, that
is, the starting point for path searches of pathnames beginning with ‘/’.
In order for a directory to become the root directory a process must have
execute (search) access for that directory.
If the current working directory is not at or under the new root direc‐
tory, it is silently set to the new root directory. It should be noted
that, on most other systems, chroot() has no effect on the process's cur‐
rent directory.
This call is restricted to the super-user.
The fchroot() function performs the same operation on an open directory
file known by the file descriptor fd.
RETURN VALUES
Upon successful completion, a value of 0 is returned. Otherwise, a value
of -1 is returned and errno is set to indicate an error.
ERRORSchroot() will fail and the root directory will be unchanged if:
[ENOTDIR] A component of the path name is not a directory.
[ENAMETOOLONG] A component of a pathname exceeded {NAME_MAX} charac‐
ters, or an entire path name exceeded {PATH_MAX} char‐
acters.
[ENOENT] The named directory does not exist.
[EACCES] Search permission is denied for any component of the
path name.
[ELOOP] Too many symbolic links were encountered in translat‐
ing the pathname.
[EFAULT] dirname points outside the process's allocated address
space.
[EIO] An I/O error occurred while reading from or writing to
the file system.
[EPERM] The effective user ID of the calling process is not
the super-user.
fchroot() will fail and the root directory will be unchanged if:
[EACCES] Search permission is denied for the directory refer‐
enced by the file descriptor.
[EBADF] The argument fd is not a valid file descriptor.
[EIO] An I/O error occurred while reading from or writing to
the file system.
[ENOTDIR] The argument fd does not reference a directory.
[EPERM] The effective user ID of the calling process is not
the super-user.
SEE ALSOchdir(2)STANDARDS
The chroot() function conforms to X/Open System Interfaces and Headers
Issue 5 (“XSH5”), with the restriction that the calling process' working
directory must be at or under the new root directory. Otherwise, the
working directory is silently set to the new root directory; this is an
extension to the standard.
chroot() was declared a legacy interface, and subsequently removed in
IEEE Std 1003.1-2001 (“POSIX.1”).
HISTORY
The chroot() function call appeared in 4.2BSD. Working directory han‐
dling was changed in NetBSD 1.4 to prevent one way a process could use a
second chroot() call to a different directory to "escape" from the
restricted subtree. The fchroot() function appeared in NetBSD 1.4.
BSD April 18, 2001 BSD