attr - extended attributes on XFS filesystem objects
SYNOPSIS
attr [ -LRq ] -s attrname [ -V attrvalue ] pathname
attr [ -LRq ] -g attrname pathname
attr [ -LRq ] -r attrname pathname
OVERVIEW
Extended attributes implement the ability for a user to
attach name:value pairs to objects within the XFS filesys
tem.
They could be used to store meta-information about the
file. For example "character-set=kanji" could tell a doc
ument browser to use the Kanji character set when display
ing that document and "thumbnail=..." could provide a
reduced resolution overview of a high resolution graphic
image.
This document describes the attr command, which is mostly
compatible with the IRIX command of the same name. It is
thus aimed specifically at users of the XFS filesystem -
for filesystem independent extended attribute manipula
tion, consult the getfattr(1) and setfattr(1) documenta
tion.
In the XFS filesystem, the names can be up to 256 bytes in
length, terminated by the first 0 byte. The intent is
that they be printable ASCII (or other character set)
names for the attribute. The values can be up to 64KB of
arbitrary binary data.
Attributes can be attached to all types of XFS inodes:
regular files, directories, symbolic links, device nodes,
etc.
XFS uses 2 disjoint attribute name spaces associated with
every filesystem object. They are the root and user
address spaces. The root address space is accessable only
to the superuser, and then only by specifying a flag argu
ment to the function call. Other users will not see or be
able to modify attributes in the root address space. The
user address space is protected by the normal file permis
sions mechanism, so the owner of the file can decide who
is able to see and/or modify the value of attributes on
any particular file.
DESCRIPTION
The attr utility allows the manipulation of extended
attributes associated with filesystem objects from within
There are four main operations that attr can perform:
GET The -g attrname option tells attr to search the
named object and print (to ssttddoouutt) the value asso
ciated with that attribute name. With the -q flag,
ssttddoouutt will be exactly and only the value of the
attribute, suitable for storage directly into a
file or processing via a piped command.
REMOVE The -r attrname option tells attr to remove an
attribute with the given name from the object if
the attribute exists. There is no output on
sucessful completion.
SET/CREATE
The -s attrname option tells attr to set the named
attribute of the object to the value read from
ssttddiinn. If an attribute with that name already
exists, its value will be replaced with this one.
If an attribute with that name does not already
exist, one will be created with this value. With
the -V attrvalue flag, the attribute will be set to
have a value of attrvalue and ssttddiinn will not be
read. With the -q flag, ssttddoouutt will not be used.
Without the -q flag, a message showing the
attribute name and the entire value will be
printed.
When the -L option is given and the named object is a sym
bolic link, operate on the attributes of the object refer
enced by the symbolic link. Without this option, operate
on the attributes of the symbolic link itself.
When the -R option is given and the process has appropri
ate privileges, operate in the root attribute namespace
rather that the USER attribute namespace.
When the -q option is given attr will try to keep quiet.
It will output error messages (to ssttddeerrrr) but will not
print status messages (to ssttddoouutt).
NOTES
The standard file interchange/archive programs tar(1), and
cpio(1) will not archive or restore extended attributes,
while the xfsdump(8) program will.
CAVEATS
The list option present in the IRIX version of this com
mand is not supported. getfattr provides a mechanism to
retrieve all of the attribute names.
getfattr(1), setfattr(1), attr_get(3), attr_set(3),
attr_multi(3), attr_remove(3), attr(5), and xfsdump(8).
Man(1) output converted with
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