freebsd-nq/usr.sbin/extattrctl/extattrctl.8

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.Dd March 30, 2000
.Dt EXTATTRCTL 8
.Os
.Sh NAME
.Nm extattrctl
.Nd manage FFS extended attributes
.Sh SYNOPSIS
.Nm extattrctl
.Cm start
.Ar path
.Nm extattrctl
.Cm stop
.Ar path
.Nm extattrctl
.Cm initattr
.Ar attrsize
.Ar attrfile
.Nm extattrctl
.Cm enable
.Ar path
.Ar attrname
.Ar attrfile
.Nm extattrctl
.Cm disable
.Ar path
.Ar attrname
.Sh DESCRIPTION
.Nm
is the management utility for extended attributes over the FFS file system.
.Nm
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
performend.  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 an FFS file system, and the FFS_EXTATTR kernel
option must have been enabled.
.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 Xo
.Cm initattr
.Op Fl p Ar path
.Op Fl r Op Ar kroa
.Op Fl w Op Ar kroa
.Ar attrsize attrfile
.Xc
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 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
The
.Fl r
and
.Fl w
options can be used to set the read and write permissions on the named
attribute, respectively.
There are four levels possible for both read and write:
.Dq k
limits reading or writing to the kernel,
.Dq r
limits activities to root,
.Dq o
limits activities to root and the owner of the file having the attribute
read or written, and
.Dq q
allows any user to perform the attribute operation.
The default is to limit activities to the root user, or
.Dq r .
.Pp
This file should not exist before running
.Cm initattr.
.It Cm enable Ar path Ar attrname Ar attrfile
Enable an attribute named
.Ar attrname
on the file system identified using
.Ar path ,
and backed by initialized attribute file
.Ar attrfile .
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 Ar attrname
Disable the attributed named
.Ar attrname
on the file system identified by
.Ar path .
The file system must have attributes started on it, and the attribute
most have been enabled using
.Cm enable .
.Sh EXAMPLES
.Pp
.Dl extattrctl start /
.Pp
Start extended attributes on the root file system.
.Pp
.Dl extattrctl initattr 17 /.attribute/md5
.Pp
Create an attribute backing file in /.attribute/md5, and set the maximum
size of each attribute to 17 bytes.  Sparse files are used for storing the
attributes, and the default permissions limiting access to the root user
are implied.
.Pp
.Dl extattrctl enable / md5 /.attribute/md5
.Pp
Enable an attribute named md5 on the root file system, backed from the file
/.attribute/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 8 ,
.Xr setextattr 8 ,
.Xr extattr 9
.Sh HISTORY
Extended attribute support was developed as part of the TrustedBSD Project,
and introduced in
.Fx 5.0 .
It was developed to support security extensions requiring additional labels
to be associated with each file or directory.
.Sh AUTHORS
Robert N M Watson