1CHROOT(2)                  Linux Programmer's Manual                 CHROOT(2)
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NAME

6       chroot - change root directory
7

SYNOPSIS

9       #include <unistd.h>
10
11       int chroot(const char *path);
12
13   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
14
15       chroot():
16           Since glibc 2.2.2:
17               _XOPEN_SOURCE && ! (_POSIX_C_SOURCE >= 200112L)
18                   || /* Since glibc 2.20: */ _DEFAULT_SOURCE
19                   || /* Glibc <= 2.19: */ _BSD_SOURCE
20           Before glibc 2.2.2:
21               none
22

DESCRIPTION

24       chroot()  changes  the  root  directory  of the calling process to that
25       specified in path.  This directory will be used for pathnames beginning
26       with /.  The root directory is inherited by all children of the calling
27       process.
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29       Only a privileged process (Linux: one with the CAP_SYS_CHROOT  capabil‐
30       ity in its user namespace) may call chroot().
31
32       This  call changes an ingredient in the pathname resolution process and
33       does nothing else.  In particular, it is not intended to  be  used  for
34       any kind of security purpose, neither to fully sandbox a process nor to
35       restrict filesystem system calls.  In the past, chroot() has been  used
36       by  daemons  to  restrict themselves prior to passing paths supplied by
37       untrusted users to system calls such as open(2).  However, if a  folder
38       is  moved  out of the chroot directory, an attacker can exploit that to
39       get out of the chroot directory as well.  The easiest way to do that is
40       to  chdir(2) to the to-be-moved directory, wait for it to be moved out,
41       then open a path like ../../../etc/passwd.
42
43       A slightly trickier variation also works under  some  circumstances  if
44       chdir(2)  is not permitted.  If a daemon allows a "chroot directory" to
45       be specified, that usually means that if you  want  to  prevent  remote
46       users  from  accessing files outside the chroot directory, you must en‐
47       sure that folders are never moved out of it.
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49       This call does not change the current working directory, so that  after
50       the call '.' can be outside the tree rooted at '/'.  In particular, the
51       superuser can escape from a "chroot jail" by doing:
52
53           mkdir foo; chroot foo; cd ..
54
55       This call does not close open file descriptors, and such file  descrip‐
56       tors may allow access to files outside the chroot tree.
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RETURN VALUE

59       On  success,  zero is returned.  On error, -1 is returned, and errno is
60       set to indicate the error.
61

ERRORS

63       Depending on the filesystem, other errors can be  returned.   The  more
64       general errors are listed below:
65
66       EACCES Search  permission  is denied on a component of the path prefix.
67              (See also path_resolution(7).)
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69       EFAULT path points outside your accessible address space.
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71       EIO    An I/O error occurred.
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73       ELOOP  Too many symbolic links were encountered in resolving path.
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75       ENAMETOOLONG
76              path is too long.
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78       ENOENT The file does not exist.
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80       ENOMEM Insufficient kernel memory was available.
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82       ENOTDIR
83              A component of path is not a directory.
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85       EPERM  The caller has insufficient privilege.
86

CONFORMING TO

88       SVr4, 4.4BSD, SUSv2 (marked LEGACY).  This  function  is  not  part  of
89       POSIX.1-2001.
90

NOTES

92       A  child  process created via fork(2) inherits its parent's root direc‐
93       tory.  The root directory is left unchanged by execve(2).
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95       The magic symbolic link, /proc/[pid]/root, can be used  to  discover  a
96       process's root directory; see proc(5) for details.
97
98       FreeBSD has a stronger jail() system call.
99

SEE ALSO

101       chroot(1), chdir(2), pivot_root(2), path_resolution(7), switch_root(8)
102

COLOPHON

104       This  page  is  part of release 5.13 of the Linux man-pages project.  A
105       description of the project, information about reporting bugs,  and  the
106       latest     version     of     this    page,    can    be    found    at
107       https://www.kernel.org/doc/man-pages/.
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111Linux                             2021-03-22                         CHROOT(2)
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