NAME
extattrctl —
manage UFS1 extended
attributes
SYNOPSIS
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 performed.
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 available 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 initialized
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.
EXAMPLES
extattrctl 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 ALSO
getextattr(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 associated with each file or directory. Backing file
autocreation was added in
NetBSD 6.0.
AUTHORS
Robert N M Watson
BUGS
extattrctl 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.