chroot

, fchroot

- change root directory

Synopsis

#include <unistd.h>

int chroot(const char *path);

int fchroot(int fildes);

Description

The chroot() and fchroot() functions cause a directory to become the root directory, the starting point for path searches for path names beginning with / (slash). The user's working directory is unaffected by the chroot() and fchroot() functions.

The path argument points to a path name naming a directory. The fildes argument to fchroot() is the open file descriptor of the directory which is to become the root.

The privilege {PRIV_PROC_CHROOT} must be asserted in the effective set of the process to change the root directory. While it is always possible to change to the system root using the fchroot() function, it is not guaranteed to succeed in any other case, even if fildes is valid in all respects.

The “. .” entry in the root directory is interpreted to mean the root directory itself. Therefore, “. .” cannot be used to access files outside the subtree rooted at the root directory. Instead, fchroot() can be used to reset the root to a directory that was opened before the root directory was changed.

Return Values

Upon successful completion, 0 is returned. Otherwise, -1 is returned, the root directory remains unchanged, and errno is set to indicate the error.

Errors

The chroot() function will fail if:

EACCES

Search permission is denied for a component of the path prefix of dirname, or search permission is denied for the directory referred to by dirname.

EBADF

The descriptor is not valid.

EFAULT

The path argument points to an illegal address.

EINVAL

The fchroot() function attempted to change to a directory the is not the system root and external circumstances do not allow this.

EINTR

A signal was caught during the execution of the chroot() function.

EIO

An I/O error occurred while reading from or writing to the file system.

ELOOP

Too many symbolic links were encountered in translating path.

ENAMETOOLONG

The length of the path argument exceeds PATH_MAX, or the length of a path component exceeds NAME_MAX while _POSIX_NO_TRUNC is in effect.

ENOENT

The named directory does not exist or is a null pathname.

ENOLINK

The path argument points to a remote machine and the link to that machine is no longer active.

ENOTDIR

Any component of the path name is not a directory.

EPERM

The {PRIV_PROC_CHROOT} privilege is not asserted in the effective set of the calling process.

See Also

chroot(1M), chdir(2), privileges(5)

Warnings

The only use of fchroot() that is appropriate is to change back to the system root.