NetBSD/usr.sbin/extattrctl/extattrctl.8

.\"	$NetBSD: extattrctl.8,v 1.5 2011/06/17 18:20:40 wiz Exp $
.\"
.\" Copyright (c) 2000-2001 Robert N. M. Watson
.\" All rights reserved.
.\"
.\" This software was developed by Robert Watson for the TrustedBSD Project.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD: src/usr.sbin/extattrctl/extattrctl.8,v 1.24 2005/02/09 18:04:40 ru Exp $
.\"
.\" Developed by the TrustedBSD Project.
.\" Support for file system extended attribute.
.\"
.Dd June 17, 2011
.Dt EXTATTRCTL 8
.Os
.Sh NAME
.Nm extattrctl
.Nd manage UFS1 extended attributes
.Sh SYNOPSIS
.Nm
.Cm start
.Ar path
.Nm
.Cm stop
.Ar path
.Nm
.Cm initattr
.Op Fl f
.Op Fl p Ar path
.Ar attrsize
.Ar attrfile
.Nm
.Cm showattr
.Ar attrfile
.Nm
.Cm enable
.Ar path
.Ar attrnamespace
.Ar attrname
.Ar attrfile
.Nm
.Cm disable
.Ar path
.Ar attrnamespace
.Ar attrname
.Sh DESCRIPTION
The
.Nm
utility
is the management utility for extended attributes over the UFS1 file system.
It allows the starting and stopping of extended attributes on a file system,
as well as initialization of attribute backing files, and enabling and
disabling of specific extended attributes on a file system.
.Pp
The first argument on the command line indicates the operation to be
performed.
Operation must be one of the following:
.Bl -tag -width indent
.It Cm start Ar path
Start extended attribute support on the file system named using
.Ar path .
The file system must be a UFS1 file system, and the
.Dv UFS_EXTATTR
kernel option must have been enabled.
If
.Pa .attribute/user
and
.Pa .attribute/system
exist at the filesystem root, extended attributes backed by files
in these directories will be automatically enabled.
Note that extended attributes can be automatically started at mount
time by using the
.Cm -o extattr
option to
.Xr mount 8 .
.It Cm stop Ar path
Stop extended attribute support on the file system named using
.Ar path .
Extended attribute support must previously have been started.
.It Cm initattr Oo Fl f Oc Oo Fl p Ar path Oc Ar attrsize attrfile
Create and initialize a file to use as an attribute backing file.
You must specify a maximum per-inode size for the attribute in bytes in
.Ar attrsize ,
as well as the file where the attribute will be stored, using
.Ar attrfile .
.Pp
The
.Fl f
argument may be used to indicate that it is alright to overwrite an
existing attribute backing file; otherwise, if the target file exists,
an error will be returned.
.Pp
The
.Fl p Ar path
argument may be used to preallocate space for all attributes rather than
relying on sparse files to conserve space.
This has the advantage of guaranteeing that space will be available
for attributes when they are written, preventing low disk space conditions
from denying attribute service.
.Pp
This file should not exist before running
.Cm initattr .
.Pp
When a user attempts to set a
.Dq user
or
.Dq system
extended attribute that lacks a backing file,
the kernel will attempt to automatically create it, provided
.Pa .attribute/user
or
.Pa .attribute/system
exist and are writable by the requesting user.
.It Cm showattr Ar attrfile
Show the attribute header values in the attribute file named by
.Ar attrfile .
.It Cm enable Ar path attrnamespace attrname attrfile
Enable an attribute named
.Ar attrname
in the namespace
.Ar attrnamespace
on the file system identified using
.Ar path ,
and backed by initialized attribute file
.Ar attrfile .
Available namespaces are
.Dq user
and
.Dq system .
The backing file must have been initialized using
.Cm initattr
before its first use.
Attributes must have been started on the file system prior to the
enabling of any attributes.
.It Cm disable Ar path attrnamespace attrname
Disable the attributed named
.Ar attrname
in namespace
.Ar attrnamespace
on the file system identified by
.Ar path .
Available namespaces are
.Dq user
and
.Dq system .
The file system must have attributes started on it, and the attribute
most have been enabled using
.Cm enable .
.El
.Sh EXAMPLES
.Dl extattrctl start /
.Pp
Start extended attributes on the root file system.
.Pp
.Dl extattrctl initattr 17 /.attribute/system/md5
.Pp
Create an attribute backing file in
.Pa /.attribute/system/md5 ,
and set the maximum size of each attribute to 17 bytes, with a
sparse file used for storing the attributes.
.Pp
.Dl extattrctl enable / system md5 /.attribute/system/md5
.Pp
Enable an attribute named md5 on the root file system, backed from the file
.Pa /.attribute/system/md5 .
.Pp
.Dl extattrctl disable / md5
.Pp
Disable the attribute named md5 on the root file system.
.Pp
.Dl extattrctl stop /
.Pp
Stop extended attributes on the root file system.
.Sh SEE ALSO
.Xr getextattr 1 ,
.Xr extattr_get_file 2 ,
.\" .Xr ffs 7 ,
.Xr extattr 9
.Sh HISTORY
Extended attribute support was developed as part of the TrustedBSD
Project, and introduced in
.Fx 5.0
and
.Nx 4.0 .
It was developed to support security extensions requiring additional
labels to be associated with each file or directory.
Backing file autocreation was added in
.Nx 6.0 .
.Sh AUTHORS
.An Robert N M Watson
.Sh BUGS
.Nm
works only on UFS1 file systems.
The kernel support for extended attribute backing files and this
control program should be generalized for any file system that
lacks native extended attribute support.