Author: wang
Date: Wed May 14 01:29:36 2014
New Revision: 1594443
URL: http://svn.apache.org/r1594443
Log:
HDFS-6283. Write end user documentation for xattrs. (wang)
Added:
hadoop/common/branches/HDFS-2006/hadoop-hdfs-project/hadoop-hdfs/src/site/apt/ExtendedAttributes.apt.vm
(with props)
Modified:
hadoop/common/branches/HDFS-2006/hadoop-hdfs-project/hadoop-hdfs/CHANGES-HDFS-2006.txt
hadoop/common/branches/HDFS-2006/hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml
Modified:
hadoop/common/branches/HDFS-2006/hadoop-hdfs-project/hadoop-hdfs/CHANGES-HDFS-2006.txt
URL:
http://svn.apache.org/viewvc/hadoop/common/branches/HDFS-2006/hadoop-hdfs-project/hadoop-hdfs/CHANGES-HDFS-2006.txt?rev=1594443&r1=1594442&r2=1594443&view=diff
==============================================================================
---
hadoop/common/branches/HDFS-2006/hadoop-hdfs-project/hadoop-hdfs/CHANGES-HDFS-2006.txt
(original)
+++
hadoop/common/branches/HDFS-2006/hadoop-hdfs-project/hadoop-hdfs/CHANGES-HDFS-2006.txt
Wed May 14 01:29:36 2014
@@ -31,7 +31,9 @@ HDFS-2006 (Unreleased)
HDFS-6377. Unify xattr name and value limits into a single limit. (wang)
- HDFS-6373. Remove support for extended attributes on symlinks (Charles
Lamb via wang)
+ HDFS-6373. Remove support for extended attributes on symlinks. (Charles
Lamb via wang)
+
+ HDFS-6283. Write end user documentation for xattrs. (wang)
OPTIMIZATIONS
Modified:
hadoop/common/branches/HDFS-2006/hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml
URL:
http://svn.apache.org/viewvc/hadoop/common/branches/HDFS-2006/hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml?rev=1594443&r1=1594442&r2=1594443&view=diff
==============================================================================
---
hadoop/common/branches/HDFS-2006/hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml
(original)
+++
hadoop/common/branches/HDFS-2006/hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml
Wed May 14 01:29:36 2014
@@ -1895,4 +1895,28 @@
</description>
</property>
-</configuration>
\ No newline at end of file
+<property>
+ <name>dfs.namenode.xattrs.enabled</name>
+ <value>true</value>
+ <description>
+ Whether support for extended attributes is enabled on the NameNode.
+ </description>
+</property>
+
+<property>
+ <name>dfs.namenode.fs-limits.max-xattrs-per-inode</name>
+ <value>32</value>
+ <description>
+ Maximum number of extended attributes per inode.
+ </description>
+</property>
+
+<property>
+ <name>dfs.namenode.fs-limits.max-xattr-size</name>
+ <value>16384</value>
+ <description>
+ The maximum combined size of the name and value of an extended attribute
in bytes.
+ </description>
+</property>
+
+</configuration>
Added:
hadoop/common/branches/HDFS-2006/hadoop-hdfs-project/hadoop-hdfs/src/site/apt/ExtendedAttributes.apt.vm
URL:
http://svn.apache.org/viewvc/hadoop/common/branches/HDFS-2006/hadoop-hdfs-project/hadoop-hdfs/src/site/apt/ExtendedAttributes.apt.vm?rev=1594443&view=auto
==============================================================================
---
hadoop/common/branches/HDFS-2006/hadoop-hdfs-project/hadoop-hdfs/src/site/apt/ExtendedAttributes.apt.vm
(added)
+++
hadoop/common/branches/HDFS-2006/hadoop-hdfs-project/hadoop-hdfs/src/site/apt/ExtendedAttributes.apt.vm
Wed May 14 01:29:36 2014
@@ -0,0 +1,98 @@
+~~ Licensed under the Apache License, Version 2.0 (the "License");
+~~ you may not use this file except in compliance with the License.
+~~ You may obtain a copy of the License at
+~~
+~~ http://www.apache.org/licenses/LICENSE-2.0
+~~
+~~ Unless required by applicable law or agreed to in writing, software
+~~ distributed under the License is distributed on an "AS IS" BASIS,
+~~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+~~ See the License for the specific language governing permissions and
+~~ limitations under the License. See accompanying LICENSE file.
+
+ ---
+ Hadoop Distributed File System-${project.version} - Extended Attributes
+ ---
+ ---
+ ${maven.build.timestamp}
+
+Extended Attributes in HDFS
+
+ \[ {{{../../index.html}Go Back}} \]
+
+%{toc|section=1|fromDepth=2|toDepth=4}
+
+* {Overview}
+
+ <Extended attributes> (abbreviated as <xattrs>) are a filesystem feature
that allow user applications to associate additional metadata with a file or
directory. Unlike system-level inode metadata such as file permissions or
modification time, extended attributes are not interpreted by the system and
are instead used by applications to store additional information about an
inode. Extended attributes could be used, for instance, to specify the
character encoding of a plain-text document.
+
+** {HDFS extended attributes}
+
+ Extended attributes in HDFS are modeled after extended attributes in Linux
(see the Linux manpage for
{{{http://www.bestbits.at/acl/man/man5/attr.txt}attr(5)}} and
{{{http://www.bestbits.at/acl/}related documentation}}). An extended attribute
is a <name-value pair>, with a string name and binary value. Xattrs names must
also be prefixed with a <namespace>. For example, an xattr named <myXattr> in
the <user> namespace would be specified as <<user.myXattr>>. Multiple xattrs
can be associated with a single inode.
+
+** {Namespaces and Permissions}
+
+ In HDFS, as in Linux, there are four valid namespaces: <<<user>>>,
<<<trusted>>>, <<<system>>>, and <<<security>>>. Each of these namespaces have
different access restrictions.
+
+ The <<<user>>> namespace is the namespace that will commonly be used by
client applications. Access to extended attributes in the user namespace is
controlled by the corresponding file permissions.
+
+ The <<<trusted>>> namespace is available only to HDFS superusers.
+
+ The <<<system>>> namespace is reserved for internal HDFS use. This namespace
is not accessible through userspace methods, and is reserved for implementing
internal HDFS features.
+
+ The <<<security>>> namespace is reserved for internal HDFS use. This
namespace is not accessible through userspace methods. It is currently unused.
+
+* {Interacting with extended attributes}
+
+ The Hadoop shell has support for interacting with extended attributes via
<<<hadoop fs -getfattr>>> and <<<hadoop fs -setfattr>>>. These commands are
styled after the Linux
{{{http://www.bestbits.at/acl/man/man1/getfattr.txt}getfattr(1)}} and
{{{http://www.bestbits.at/acl/man/man1/setfattr.txt}setfattr(1)}} commands.
+
+** {getfattr}
+
+ <<<hadoop fs -getfattr [-R] {-n name | -d} [-e en] <path>>>>
+
+ Displays the extended attribute names and values (if any) for a file or
directory.
+
+*--+--+
+-R | Recursively list the attributes for all files and directories.
+*--+--+
+-n name | Dump the named extended attribute value.
+*--+--+
+-d | Dump all extended attribute values associated with pathname.
+*--+--+
+-e \<encoding\> | Encode values after retrieving them. Valid encodings are
"text", "hex", and "base64". Values encoded as text strings are enclosed in
double quotes ("), and values encoded as hexadecimal and base64 are prefixed
with 0x and 0s, respectively.
+*--+--+
+\<path\> | The file or directory.
+*--+--+
+
+** {setfattr}
+
+ <<<hadoop fs -setfattr {-n name [-v value] | -x name} <path>>>>
+
+ Sets an extended attribute name and value for a file or directory.
+
+*--+--+
+-n name | The extended attribute name.
+*--+--+
+-v value | The extended attribute value. There are three different encoding
methods for the value. If the argument is enclosed in double quotes, then the
value is the string inside the quotes. If the argument is prefixed with 0x or
0X, then it is taken as a hexadecimal number. If the argument begins with 0s or
0S, then it is taken as a base64 encoding.
+*--+--+
+-x name | Remove the extended attribute.
+*--+--+
+\<path\> | The file or directory.
+*--+--+
+
+* {Configuration options}
+
+
+ HDFS supports extended attributes out of the box, without additional
configuration. Administrators could potentially be interested in the options
limiting the number of xattrs per inode and the size of xattrs, since xattrs
increase the on-disk and in-memory space consumption of an inode.
+
+ * <<<dfs.namenode.xattrs.enabled>>>
+
+ Whether support for extended attributes is enabled on the NameNode. By
default, extended attributes are enabled.
+
+ * <<<dfs.namenode.fs-limits.max-xattrs-per-inode>>>
+
+ The maximum number of extended attributes per inode. By default, this limit
is 32.
+
+ * <<<dfs.namenode.fs-limits.max-xattr-size>>>
+
+ The maximum combined size of the name and value of an extended attribute in
bytes. By default, this limit is 16384 bytes.
Propchange:
hadoop/common/branches/HDFS-2006/hadoop-hdfs-project/hadoop-hdfs/src/site/apt/ExtendedAttributes.apt.vm
------------------------------------------------------------------------------
svn:eol-style = native
