EXTATTRCTL(8) BSD System Manager's Manual EXTATTRCTL(8)NAMEextattrctl — manage UFS1 extended attributes
SYNOPSISextattrctl start path
extattrctl stop path
extattrctl initattr [-f] [-p path] attrsize attrfile
extattrctl showattr attrfile
extattrctl enable path attrnamespace attrname attrfile
extattrctl disable path attrnamespace attrname
DESCRIPTION
The extattrctl 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.
The first argument on the command line indicates the operation to be per‐
formed. Operation must be one of the following:
start path
Start extended attribute support on the file system named using
path. The file system must be a UFS1 file system, and the
UFS_EXTATTR kernel option must have been enabled. If
.attribute/user and .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 -o extattr
option to mount(8).
stop path
Stop extended attribute support on the file system named using
path. Extended attribute support must previously have been
started.
initattr [-f] [-p path] 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 attrsize, as well as the file where the attribute will
be stored, using attrfile.
The -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.
The -p 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 avail‐
able for attributes when they are written, preventing low disk
space conditions from denying attribute service.
This file should not exist before running initattr.
When a user attempts to set a “user” or “system” extended
attribute that lacks a backing file, the kernel will attempt to
automatically create it, provided .attribute/user or
.attribute/system exist and are writable by the requesting user.
showattr attrfile
Show the attribute header values in the attribute file named by
attrfile.
enable path attrnamespace attrname attrfile
Enable an attribute named attrname in the namespace attrnamespace
on the file system identified using path, and backed by initial‐
ized attribute file attrfile. Available namespaces are “user”
and “system”. The backing file must have been initialized using
initattr before its first use. Attributes must have been started
on the file system prior to the enabling of any attributes.
disable path attrnamespace attrname
Disable the attributed named attrname in namespace attrnamespace
on the file system identified by path. Available namespaces are
“user” and “system”. The file system must have attributes
started on it, and the attribute most have been enabled using
enable.
EXAMPLESextattrctl start /
Start extended attributes on the root file system.
extattrctl initattr 17 /.attribute/system/md5
Create an attribute backing file in /.attribute/system/md5, and set the
maximum size of each attribute to 17 bytes, with a sparse file used for
storing the attributes.
extattrctl enable / system md5 /.attribute/system/md5
Enable an attribute named md5 on the root file system, backed from the
file /.attribute/system/md5.
extattrctl disable / md5
Disable the attribute named md5 on the root file system.
extattrctl stop /
Stop extended attributes on the root file system.
SEE ALSOgetextattr(1), extattr_get_file(2), extattr(9)HISTORY
Extended attribute support was developed as part of the TrustedBSD
Project, and introduced in FreeBSD 5.0 and NetBSD 4.0. It was developed
to support security extensions requiring additional labels to be associ‐
ated with each file or directory. Backing file autocreation was added in
NetBSD 6.0.
AUTHORS
Robert N M Watson
BUGSextattrctl works only on UFS1 file systems. The kernel support for
extended attribute backing files and this control program should be gen‐
eralized for any file system that lacks native extended attribute sup‐
port.
BSD June 17, 2011 BSD
