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).


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