attr(1) - f36

1ATTR(1)                      XFS Compatibility API                     ATTR(1)
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NAME

6       attr - extended attributes on XFS filesystem objects
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SYNOPSIS

9       attr [ -LRSq ] -s attrname [ -V attrvalue ] pathname
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11       attr [ -LRSq ] -g attrname pathname
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13       attr [ -LRSq ] -r attrname pathname
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15       attr [ -LRSq ] -l pathname
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OVERVIEW

19       Extended  attributes  implement  the  ability  for  a  user  to  attach
20       name:value pairs to objects within the XFS filesystem.
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22       This document describes the attr command, which  is  mostly  compatible
23       with  the IRIX command of the same name.  It is thus aimed specifically
24       at users of the XFS filesystem - for  filesystem  independent  extended
25       attribute  manipulation,  consult the getfattr(1) and setfattr(1) docu‐
26       mentation.
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28       Extended attributes can be used to  store  meta-information  about  the
29       file.   For example "character-set=kanji" could tell a document browser
30       to use the Kanji  character  set  when  displaying  that  document  and
31       "thumbnail=..."  could  provide a reduced resolution overview of a high
32       resolution graphic image.
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34       In the XFS filesystem, the names can be up to 256 bytes in length, ter‐
35       minated  by  the  first  0  byte.  The intent is that they be printable
36       ASCII (or other character set) names for the attribute.  The values can
37       be up to 64KB of arbitrary binary data.
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39       Attributes  can  be attached to all types of XFS inodes: regular files,
40       directories, symbolic links, device nodes, etc.
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42       XFS uses  2  disjoint  attribute  name  spaces  associated  with  every
43       filesystem  object.   They  are  the root and user address spaces.  The
44       root address space is accessible only to the superuser, and  then  only
45       by  specifying  a flag argument to the function call.  Other users will
46       not see or be able to modify attributes in the root address space.  The
47       user  address  space is protected by the normal file permissions mecha‐
48       nism, so the owner of the file can decide who is  able  to  see  and/or
49       modify the value of attributes on any particular file.
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DESCRIPTION

52       The attr utility allows the manipulation of extended attributes associ‐
53       ated with filesystem objects from within shell scripts.
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55       There are four main operations that attr can perform:
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57       GET    The -g attrname option tells attr to search the named object and
58              print (to stdout) the value associated with that attribute name.
59              With the -q flag, stdout will be exactly and only the  value  of
60              the attribute, suitable for storage directly into a file or pro‐
61              cessing via a piped command.
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63       LIST   The -l option tells attr to list the names of all the attributes
64              that  are associated with the object, and the number of bytes in
65              the value of each of those attributes.  With the -q flag, stdout
66              will be a simple list of only the attribute names, one per line,
67              suitable for input into a script.
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69       REMOVE The -r attrname option tells attr to remove  an  attribute  with
70              the  given  name from the object if the attribute exists.  There
71              is no output on successful completion.
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73       SET/CREATE
74              The -s attrname option tells attr to set the named attribute  of
75              the  object  to the value read from stdin.  If an attribute with
76              that name already exists, its value will be replaced  with  this
77              one.  If an attribute with that name does not already exist, one
78              will be created with this value.  With the  -V  attrvalue  flag,
79              the attribute will be set to have a value of attrvalue and stdin
80              will not be read.  With the -q flag, stdout will  not  be  used.
81              Without  the  -q  flag, a message showing the attribute name and
82              the entire value will be printed.
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84       When the -L option is given and the named object is  a  symbolic  link,
85       operate  on  the  attributes  of  the object referenced by the symbolic
86       link.  Without this option, operate on the attributes of  the  symbolic
87       link itself.
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89       When the -R option is given and the process has appropriate privileges,
90       operate in the root attribute namespace rather that the USER  attribute
91       namespace.
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93       The  -S  option is similar, except it specifies use of the security at‐
94       tribute namespace.
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96       When the -q option is given attr will try to keep quiet.  It will  out‐
97       put  error  messages (to stderr) but will not print status messages (to
98       stdout).
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NOTES

101       The standard file interchange/archive programs tar(1), and cpio(1) will
102       not  archive  or restore extended attributes, while the xfsdump(8) pro‐
103       gram will.
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CAVEATS

106       The list option present in the IRIX version of this command is not sup‐
107       ported.  getfattr provides a mechanism to retrieve all of the attribute
108       names.
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AUTHOR

111       Andreas Gruenbacher, <andreas.gruenbacher@gmail.com> and  the  SGI  XFS
112       development team, <linux-xfs@oss.sgi.com>.
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114       Please   send   your   bug   reports  or  comments  to  <https://savan‐
115       nah.nongnu.org/bugs/?group=attr> or <acl-devel@nongnu.org>.
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