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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | STANDARDS | HISTORY | NOTES | SEE ALSO | COLOPHON |
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chroot(2) System Calls Manual chroot(2)
chroot - change root directory
Standard C library (libc, -lc)
#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:
_XOPEN_SOURCE && ! (_POSIX_C_SOURCE >= 200112L)
|| /* Since glibc 2.20: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE
Before glibc 2.2.2:
none
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 in its user namespace) may call chroot().
This call changes an ingredient in the pathname resolution
process and does nothing else. In particular, it is not intended
to be used for any kind of security purpose, neither to fully
sandbox a process nor to restrict filesystem system calls. In
the past, chroot() has been used by daemons to restrict
themselves prior to passing paths supplied by untrusted users to
system calls such as open(2). However, if a folder is moved out
of the chroot directory, an attacker can exploit that to get out
of the chroot directory as well. The easiest way to do that is
to chdir(2) to the to-be-moved directory, wait for it to be moved
out, then open a path like ../../../etc/passwd.
A slightly trickier variation also works under some circumstances
if chdir(2) is not permitted. If a daemon allows a "chroot
directory" to be specified, that usually means that if you want
to prevent remote users from accessing files outside the chroot
directory, you must ensure that folders are never moved out of
it.
This call does not change the current working directory, so that
after the call '.' can be outside the tree rooted at '/'. 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.
On success, zero is returned. On error, -1 is returned, and
errno is set to indicate the error.
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.
None.
SVr4, 4.4BSD, SUSv2 (marked LEGACY). This function is not part
of POSIX.1-2001.
A child process created via fork(2) inherits its parent's root
directory. The root directory is left unchanged by execve(2).
The magic symbolic link, /proc/pid/root, can be used to discover
a process's root directory; see proc(5) for details.
FreeBSD has a stronger jail() system call.
chroot(1), chdir(2), pivot_root(2), path_resolution(7),
switch_root(8)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.9.1.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2024-06-26. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.9.1 2024-05-02 chroot(2)
Pages that refer to this page: capsh(1), chroot(1), dpkg(1), nsenter(1), systemd-detect-virt(1), chdir(2), clone(2), getrandom(2), mount(2), openat2(2), pivot_root(2), syscalls(2), unshare(2), cap_launch(3), getcwd(3), syslog(3), system(3), core(5), proc(5), proc_pid_mountinfo(5), proc_pid_root(5), systemd.exec(5), capabilities(7), path_resolution(7), pthreads(7), lloadd(8), slapd(8), switch_root(8)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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