Section (1) chown
Name
chown — change file owner and group
Synopsis
chown
[OPTION
...] [OWNER][:[GROUP]
] FILE
...
chown
[OPTION
...] −−reference
=RFILE
FILE
...
DESCRIPTION
This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files_zsingle_quotesz_ group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user_zsingle_quotesz_s login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed.
OPTIONS
Change the owner and/or group of each FILE to OWNER and/or
GROUP. With −−reference
, change the owner and
group of each FILE to those of RFILE.
−c
,−−changes
-
like verbose but report only when a change is made
−f
,−−silent
,−−quiet
-
suppress most error messages
−v
,−−verbose
-
output a diagnostic for every file processed
−−dereference
-
affect the referent of each symbolic link (this is the default), rather than the symbolic link itself
−h
,−−no−dereference
-
affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink)
−−from
=CURRENT_OWNER/:CURRENT_GROUP-
change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute
−−no−preserve−root
-
do not treat _zsingle_quotesz_/_zsingle_quotesz_ specially (the default)
−−preserve−root
-
fail to operate recursively on _zsingle_quotesz_/_zsingle_quotesz_
−−reference
=RFILE/-
use RFILE_zsingle_quotesz_s owner and group rather than specifying OWNER:GROUP values
−R
,−−recursive
-
operate on files and directories recursively
The following options modify how a hierarchy is traversed
when the −R
option is also
specified. If more than one is specified, only the final one
takes effect.
−H
-
if a command line argument is a symbolic link to a directory, traverse it
−L
-
traverse every symbolic link to a directory encountered
−P
-
do not traverse any symbolic links (default)
−−help
-
display this help and exit
−−version
-
output version information and exit
Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a _zsingle_quotesz_:_zsingle_quotesz_ following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic.
EXAMPLES
chown root /u
Change the owner of /u to root.
chown root:staff /u
Likewise, but also change its group to staff.
chown −hR root /u
Change the owner of /u and subfiles to root.
REPORTING BUGS
GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
Report any translation bugs to <https://translationproject.org/team/>
SEE ALSO
Full documentation <https://www.gnu.org/software/coreutils/chown>
or available locally via: info _zsingle_quotesz_(coreutils) chown invocation_zsingle_quotesz_
COPYRIGHT |
---|
Copyright © 2019 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://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. |
Section (2) chown
Name
chown, fchown, lchown, fchownat — change ownership of a file
Synopsis
#include <unistd.h>
int
chown( |
const char *pathname, |
uid_t owner, | |
gid_t group) ; |
int
fchown( |
int fd, |
uid_t owner, | |
gid_t group) ; |
int
lchown( |
const char *pathname, |
uid_t owner, | |
gid_t group) ; |
#include <fcntl.h> /* Definition of AT_* constants */ #include <unistd.h>
int
fchownat( |
int dirfd, |
const char *pathname, | |
uid_t owner, | |
gid_t group, | |
int flags) ; |
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Note | |||||||||
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|
DESCRIPTION
These system calls change the owner and group of a file.
The chown
(), fchown
(), and lchown
() system calls differ only in how
the file is specified:
-
chown
() changes the ownership of the file specified bypathname
, which is dereferenced if it is a symbolic link. -
fchown
() changes the ownership of the file referred to by the open file descriptorfd
. -
lchown
() is likechown
(), but does not dereference symbolic links.
Only a privileged process (Linux: one with the
CAP_CHOWN
capability) may
change the owner of a file. The owner of a file may change
the group of the file to any group of which that owner is a
member. A privileged process (Linux: with CAP_CHOWN
) may change the group
arbitrarily.
If the owner
or
group
is specified as
−1, then that ID is not changed.
When the owner or group of an executable file is changed
by an unprivileged user, the S_ISUID
and S_ISGID
mode bits are cleared. POSIX does
not specify whether this also should happen when root does
the chown
(); the Linux behavior
depends on the kernel version, and since Linux 2.2.13, root
is treated like other users. In case of a
non-group-executable file (i.e., one for which the
S_IXGRP
bit is not set) the
S_ISGID
bit indicates mandatory
locking, and is not cleared by a chown
().
When the owner or group of an executable file is changed (by any user), all capability sets for the file are cleared.
fchownat()
The fchownat
() system call
operates in exactly the same way as chown
(), except for the differences
described here.
If the pathname given in pathname
is relative, then it
is interpreted relative to the directory referred to by the
file descriptor dirfd
(rather than relative
to the current working directory of the calling process, as
is done by chown
() for a
relative pathname).
If pathname
is
relative and dirfd
is the special value AT_FDCWD
, then pathname
is interpreted
relative to the current working directory of the calling
process (like chown
()).
If pathname
is
absolute, then dirfd
is ignored.
The flags
argument is a bit mask created by ORing together 0 or more
of the following values;
AT_EMPTY_PATH
(since Linux 2.6.39)-
If
pathname
is an empty string, operate on the file referred to bydirfd
(which may have been obtained using the open(2)O_PATH
flag). In this case,dirfd
can refer to any type of file, not just a directory. Ifdirfd
isAT_FDCWD
, the call operates on the current working directory. This flag is Linux-specific; define_GNU_SOURCE
to obtain its definition. AT_SYMLINK_NOFOLLOW
-
If
pathname
is a symbolic link, do not dereference it: instead operate on the link itself, likelchown
(). (By default,fchownat
() dereferences symbolic links, likechown
().)
See openat(2) for an
explanation of the need for fchownat
().
RETURN VALUE
On success, zero is returned. On error, −1 is
returned, and errno
is set
appropriately.
ERRORS
Depending on the filesystem, errors other than those listed below can be returned.
The more general errors for chown
() are listed below.
- EACCES
-
Search permission is denied on a component of the path prefix. (See also path_resolution(7).)
- EFAULT
-
pathname
points outside your accessible address space. - ELOOP
-
Too many symbolic links were encountered in resolving
pathname
. - ENAMETOOLONG
-
pathname
is too long. - ENOENT
-
The file does not exist.
- ENOMEM
-
Insufficient kernel memory was available.
- ENOTDIR
-
A component of the path prefix is not a directory.
- EPERM
-
The calling process did not have the required permissions (see above) to change owner and/or group.
- EPERM
-
The file is marked immutable or append-only. (See ioctl_iflags(2).)
- EROFS
-
The named file resides on a read-only filesystem.
The general errors for fchown
() are listed below:
- EBADF
-
fd
is not a valid open file descriptor. - EIO
-
A low-level I/O error occurred while modifying the inode.
- ENOENT
-
See above.
- EPERM
-
See above.
- EROFS
-
See above.
The same errors that occur for chown
() can also occur for fchownat
(). The following additional errors
can occur for fchownat
():
- EBADF
-
dirfd
is not a valid file descriptor. - EINVAL
-
Invalid flag specified in
flags
. - ENOTDIR
-
pathname
is relative anddirfd
is a file descriptor referring to a file other than a directory.
VERSIONS
fchownat
() was added to
Linux in kernel 2.6.16; library support was added to glibc in
version 2.4.
CONFORMING TO
chown
(), fchown
(), lchown
(): 4.4BSD, SVr4, POSIX.1-2001,
POSIX.1-2008.
The 4.4BSD version can be used only by the superuser (that is, ordinary users cannot give away files).
fchownat
():
POSIX.1-2008.
NOTES
Ownership of new files
When a new file is created (by, for example, open(2) or mkdir(2)), its owner is
made the same as the filesystem user ID of the creating
process. The group of the file depends on a range of
factors, including the type of filesystem, the options used
to mount the filesystem, and whether or not the
set-group-ID mode bit is enabled on the parent directory.
If the filesystem supports the −o grpid
(or, synonymously
−o bsdgroups
) and
−o nogrpid
(or,
synonymously −o
sysvgroups
) mount(8) options, then
the rules are as follows:
-
If the filesystem is mounted with
−o grpid
, then the group of a new file is made the same as that of the parent directory. -
If the filesystem is mounted with
−o nogrpid
and the set-group-ID bit is disabled on the parent directory, then the group of a new file is made the same as the process_zsingle_quotesz_s filesystem GID. -
If the filesystem is mounted with
−o nogrpid
and the set-group-ID bit is enabled on the parent directory, then the group of a new file is made the same as that of the parent directory.
As at Linux 4.12, the −o
grpid
and −o
nogrpid
mount options are supported by ext2, ext3,
ext4, and XFS. Filesystems that don_zsingle_quotesz_t support these mount
options follow the −o
nogrpid
rules.
Glibc notes
On older kernels where fchownat
() is unavailable, the glibc
wrapper function falls back to the use of chown
() and lchown
(). When pathname
is a relative
pathname, glibc constructs a pathname based on the symbolic
link in /proc/self/fd
that
corresponds to the dirfd
argument.
NFS
The chown
() semantics are
deliberately violated on NFS filesystems which have UID
mapping enabled. Additionally, the semantics of all system
calls which access the file contents are violated, because
chown
() may cause immediate
access revocation on already open files. Client side
caching may lead to a delay between the time where
ownership have been changed to allow access for a user and
the time where the file can actually be accessed by the
user on other clients.
Historical details
The original Linux chown
(), fchown
(), and lchown
() system calls supported only
16-bit user and group IDs. Subsequently, Linux 2.4 added
chown32
(), fchown32
(), and lchown32
(), supporting 32-bit IDs. The
glibc chown
(), fchown
(), and lchown
() wrapper functions transparently
deal with the variations across kernel versions.
In versions of Linux prior to 2.1.81 (and distinct from
2.1.46), chown
() did not
follow symbolic links. Since Linux 2.1.81, chown
() does follow symbolic links, and
there is a new system call lchown
() that does not follow symbolic
links. Since Linux 2.1.86, this new call (that has the same
semantics as the old chown
())
has got the same syscall number, and chown
() got the newly introduced
number.
EXAMPLE
The following program changes the ownership of the file named in its second command-line argument to the value specified in its first command-line argument. The new owner can be specified either as a numeric user ID, or as a username (which is converted to a user ID by using getpwnam(3) to perform a lookup in the system password file).
Program source
#include <pwd.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> int main(int argc, char *argv[]) { uid_t uid; struct passwd *pwd; char *endptr; if (argc != 3 || argv[1][0] == _zsingle_quotesz_ _zsingle_quotesz_) { fprintf(stderr, %s <owner> <file> , argv[0]); exit(EXIT_FAILURE); } uid = strtol(argv[1], &endptr, 10); /* Allow a numeric string */ if (*endptr != _zsingle_quotesz_ _zsingle_quotesz_) { /* Was not pure numeric string */ pwd = getpwnam(argv[1]); /* Try getting UID for username */ if (pwd == NULL) { perror(getpwnam); exit(EXIT_FAILURE); } uid = pwd−>pw_uid; } if (chown(argv[2], uid, −1) == −1) { perror(chown); exit(EXIT_FAILURE); } exit(EXIT_SUCCESS); }
COLOPHON
This page is part of release 5.04 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/.
Copyright (c) 1992 Drew Eckhardt (drewcs.colorado.edu), March 28, 1992 and Copyright (c) 1998 Andries Brouwer (aebcwi.nl) and Copyright (c) 2006, 2007, 2008, 2014 Michael Kerrisk <mtk.manpagesgmail.com> %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. %%%LICENSE_END Modified by Michael Haardt <michaelmoria.de> Modified 1993-07-21 by Rik Faith <faithcs.unc.edu> Modified 1996-07-09 by Andries Brouwer <aebcwi.nl> Modified 1996-11-06 by Eric S. Raymond <esrthyrsus.com> Modified 1997-05-18 by Michael Haardt <michaelcantor.informatik.rwth-aachen.de> Modified 2004-06-23 by Michael Kerrisk <mtk.manpagesgmail.com> 2007-07-08, mtk, added an example program; updated SYNOPSIS 2008-05-08, mtk, Describe rules governing ownership of new files (bsdgroups versus sysvgroups, and the effect of the parent directory_zsingle_quotesz_s set-group-ID mode bit). |