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[MAN] chroot

Content-type: text/html; charset=UTF-8 Man page of CHROOT

CHROOT

Section: Linux Programmer's Manual (2)
Updated: 2017-09-15
Index Return to Main Contents
 

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:
_XOPEN_SOURCE && ! (_POSIX_C_SOURCE >= 200112L)
    || /* Since glibc 2.20: */ _DEFAULT_SOURCE
    || /* Glibc versions <= 2.19: */ _BSD_SOURCE
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 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.  

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

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

COLOPHON

This page is part of release 4.15 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
CONFORMING TO
NOTES
SEE ALSO
COLOPHON

This document was created by man2html, using the manual pages.
Time: 04:45:35 GMT, September 16, 2022 Content-type: text/html; charset=UTF-8 Man page of CHROOT

CHROOT

Section: User Commands (8)
Updated: January 2018
Index Return to Main Contents
 

NAME

chroot - run command or interactive shell with special root directory  

SYNOPSIS

chroot [,OPTION/] ,NEWROOT /[,COMMAND /[,ARG/]...]
chroot ,OPTION/  

DESCRIPTION

Run COMMAND with root directory set to NEWROOT.

--groups=,G_LIST/
specify supplementary groups as g1,g2,..,gN
--userspec=,USER/:GROUP
specify user and group (ID or name) to use
--skip-chdir
do not change working directory to '/'
--help
display this help and exit
--version
output version information and exit

If no command is given, run '"$SHELL" -i' (default: '/bin/sh -i').  

AUTHOR

Written by Roland McGrath.  

REPORTING BUGS

GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
Report chroot translation bugs to <http://translationproject.org/team/>  

COPYRIGHT

Copyright © 2017 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.  

SEE ALSO

chroot(2)


Full documentation at: <http://www.gnu.org/software/coreutils/chroot>
or available locally via: info '(coreutils) chroot invocation'


 

Index

NAME
SYNOPSIS
DESCRIPTION
AUTHOR
REPORTING BUGS
COPYRIGHT
SEE ALSO

This document was created by man2html, using the manual pages.
Time: 04:46:01 GMT, September 16, 2022

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