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Name

chroot - change root directory

Synopsis

#include <unistd.h>

int chroot(const char *path);

Feature Test Macro Requirements for glibc (see feature_test_macros(7) ):

chroot():

Since glibc 2.2.2: 

_BSD_SOURCE ||
    (_XOPEN_SOURCE >= 500 ||
        _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED) &&
    !(_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600)
Before glibc 2.2.2: none

Description

chroot() changes the root directory of the calling process to that specified in path. This directory will be used for pathnames beginning with /. The root directory is inherited by all children of the calling process.

Only a privileged process (Linux: one with the CAP_SYS_CHROOT capability) may call chroot().

This call changes an ingredient in the pathname resolution process and does nothing else.

This call does not change the current working directory, so that after the call aq.aq can be outside the tree rooted at aq/aq. In particular, the superuser can escape from a "chroot jail" by doing: 

    mkdir foo; chroot foo; cd ..

This call does not close open file descriptors, and such file descriptors may allow access to files outside the chroot tree.

Return Value

On success, zero is returned. On error, -1 is returned, and errno is set appropriately.

Errors

Depending on the filesystem, other errors can be returned. The more general errors are listed below:
EACCES
Search permission is denied on a component of the path prefix. (See also path_resolution(7) .)
EFAULT
path points outside your accessible address space.
EIO
An I/O error occurred.
ELOOP
Too many symbolic links were encountered in resolving path.
ENAMETOOLONG
path is too long.
ENOENT
The file does not exist.
ENOMEM
Insufficient kernel memory was available.
ENOTDIR
A component of path is not a directory.
EPERM
The caller has insufficient privilege.

Conforming to

SVr4, 4.4BSD, SUSv2 (marked LEGACY). This function is not part of POSIX.1-2001.

Notes

A child process created via fork(2) inherits its parent’s root directory. The root directory is left unchanged by execve(2) .

FreeBSD has a stronger jail() system call.

See Also

chdir(2) , path_resolution(7)

Colophon

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