Section: Linux Programmer's Manual (2)
chroot - change root directory
int chroot(const char *path);
Feature Test Macro Requirements for glibc (see
- Since glibc 2.2.2:
_XOPEN_SOURCE && ! (_POSIX_C_SOURCE >= 200112L)
|| /* Since glibc 2.20: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE
- Before glibc 2.2.2: none
changes the root directory of the calling process to that specified in
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
capability in its user namespace) may call
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,
has been used by daemons to restrict themselves prior to passing paths
supplied by untrusted users to system calls such as
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
to the to-be-moved directory, wait for it to be moved out, then open a
path like ../../../etc/passwd.
trickier variation also works under some circumstances if
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"
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
is set appropriately.
Depending on the filesystem, other errors can be returned.
The more general errors are listed below:
Search permission is denied on a component of the path prefix.
points outside your accessible address space.
An I/O error occurred.
Too many symbolic links were encountered in resolving
is too long.
The file does not exist.
Insufficient kernel memory was available.
A component of
is not a directory.
The caller has insufficient privilege.
SVr4, 4.4BSD, SUSv2 (marked LEGACY).
This function is not part of POSIX.1-2001.
A child process created via
inherits its parent's root directory.
The root directory is left unchanged by
The magic symbolic link,
can be used to discover a process's root directory; see
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