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chroot(2) — Linux manual page

NAME \|LIBRARY \|SYNOPSIS \|DESCRIPTION \|RETURN VALUE \|ERRORS \|STANDARDS \|HISTORY \|NOTES \|SEE ALSO \|COLOPHON

chroot(2)                  System Calls Manualchroot(2)

NAME top

       chroot - change root directory

LIBRARY top

       Standard C library (libc,-lc)

SYNOPSIS top

#include <unistd.h>int chroot(const char *path);   Feature Test Macro Requirements for glibc (seefeature_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

DESCRIPTION top

chroot() changes the root directory of the calling process to that specified inpath. 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 theCAP_SYS_CHROOT capability in its user namespace) may callchroot(). 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 asopen(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 tochdir(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 ifchdir(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.

RETURN VALUE top

       On success, zero is returned.  On error, -1 is returned, anderrno       is set to indicate the error.

ERRORS top

       Depending on the filesystem, other errors can be returned.  The       more general errors are listed below:EACCESSearch permission is denied on a component of the path              prefix.  (See alsopath_resolution(7).)EFAULTpath points outside your accessible address space.EIOAn I/O error occurred.ELOOPToo many symbolic links were encountered in resolvingpath.ENAMETOOLONGpath is too long.ENOENTThe file does not exist.ENOMEMInsufficient kernel memory was available.ENOTDIR              A component ofpath is not a directory.EPERMThe caller has insufficient privilege.

STANDARDS top

       None.

HISTORY top

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

NOTES top

       A child process created viafork(2) inherits its parent's root       directory.  The root directory is left unchanged byexecve(2).       The magic symbolic link,/proc/pid/root, can be used to discover a       process's root directory; seeproc(5) for details.       FreeBSD has a strongerjail() system call.

COLOPHON top

       This page is part of theman-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-6.15.tar.gz       fetched from       ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on       2025-08-11.  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 isnot       part of the original manual page), send a mail to       man-pages@man7.orgLinux man-pages 6.15            2025-05-17chroot(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)