attr - extended attributes on XFS filesystem objects
attr [ -LRSq ] -s attrname [ -V attrvalue ]
attr [ -LRSq ] -g attrname pathname
attr [ -LRSq ] -r attrname pathname
attr [ -LRSq ] -l pathname
Extended attributes implement the ability for a user to attach name:value pairs
to objects within the XFS filesystem.
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
manipulation, consult the getfattr(1)
Extended attributes can be used to store meta-information about the file. For
example "character-set=kanji" could tell a document browser to use
the Kanji character set when displaying that document and
"thumbnail=..." could provide a reduced resolution overview of a
high resolution graphic image.
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
address spaces. The
address space is accessible only to the superuser, and then only
by specifying a flag argument to the function call. Other users will not see
or be able to modify attributes in the root
address space. The
address space is protected by the normal file permissions
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.
utility allows the manipulation of extended attributes
associated with filesystem objects from within shell scripts.
There are four main operations that attr
- The -g attrname option tells attr to search
the named object and print (to stdout) the value associated with that
attribute name. With the -q flag, stdout will be exactly and only
the value of the attribute, suitable for storage directly into a file or
processing via a piped command.
- The -l option tells attr to list the names of
all the attributes that are associated with the object, and the number of
bytes in the value of each of those attributes. With the -q flag,
stdout will be a simple list of only the attribute names, one per line,
suitable for input into a script.
- 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 successful completion.
- The -s attrname option tells attr to set the
named attribute of the object to the value read from stdin. 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 stdin will
not be read. With the -q flag, stdout 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 symbolic link,
operate on the attributes of the object referenced 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 appropriate privileges,
operate in the root
attribute namespace rather that the USER
option is similar, except it specifies use of the security
When the -q
option is given attr
will try to keep quiet. It will
output error messages (to stderr) but will not print status messages (to
The standard file interchange/archive programs tar(1)
, and cpio(1)
will not archive or restore extended attributes, while the xfsdump(8)
The list option present in the IRIX version of this command is not supported.
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).