http://hadoop.apache.org/docs/r2.4.1/hadoop-project-dist/hadoop-hdfs/HdfsPermissionsGuide.html#Group_Mapping

Mostly a cut-and-paste from core-default.xml, which has some very good descriptive text for the org.apache.hadoop.security.JniBasedUnixGroupsMappingWithFallback implementation behavior.

Let me know how it looks to you.

Thanks Ray Chiang for the patch! Some comments:
1.

+   the <code>bash -c groups</code> command to resolve a list of

<code> and </code> should be <<< and >>>. Most of Hadoop documents are now written in APT format (*.apt.vm). The format is described in http://maven.apache.org/doxia/references/apt-format.html

2.

+   This implementation shells out to the Linux/Unix environment with

ShellBasedUnixGroupsMappings now supports Windows also.

3 (minor).

+   JNI is available the implementation will use the API within hadoop

I think it's better to add a comma(,) between 'available' and 'the'.

Akira Ajisaka, thanks for the quick feedback. I've incorporated your suggestions.

Thanks for the update!

+   This implementation shells out with the the <<<bash -c groups>>>

Would you please remove duplicated 'the'? Other than that, the patch looks good to me.

Last fix.

Submit for testing.

+1 (non-binding), pending Jenkins.

+1 overall. Here are the results of testing the latest attachment
http://issues.apache.org/jira/secure/attachment/12660925/HDFS6664-03.patch
against trunk revision .

+1 @author. The patch does not contain any @author tags.

+0 tests included. The patch appears to be a documentation patch that doesn't require tests.

+1 javac. The applied patch does not increase the total number of javac compiler warnings.

+1 javadoc. There were no new javadoc warning messages.

+1 eclipse:eclipse. The patch built with eclipse:eclipse.

+1 findbugs. The patch does not introduce any new Findbugs (version 2.0.3) warnings.

+1 release audit. The applied patch does not increase the total number of release audit warnings.

+1 core tests. The patch passed unit tests in hadoop-hdfs-project/hadoop-hdfs.

+1 contrib tests. The patch passed contrib unit tests.

Test results: https://builds.apache.org/job/PreCommit-HDFS-Build/7606//testReport/
Console output: https://builds.apache.org/job/PreCommit-HDFS-Build/7606//console

This message is automatically generated.

+1 lgtm.

Committing to trunk and branch-2.

Thanks!

SUCCESS: Integrated in Hadoop-trunk-Commit #6124 (See https://builds.apache.org/job/Hadoop-trunk-Commit/6124/)
HDFS-6664. HDFS permissions guide documentation states incorrect default group mapping class. (Ray Chiang via aw) (aw: rev 3a1f981686835f64df4498f93dae73fde3f2c7a8)

• hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
• hadoop-hdfs-project/hadoop-hdfs/src/site/apt/HdfsPermissionsGuide.apt.vm

FAILURE: Integrated in Hadoop-Yarn-trunk #693 (See https://builds.apache.org/job/Hadoop-Yarn-trunk/693/)
HDFS-6664. HDFS permissions guide documentation states incorrect default group mapping class. (Ray Chiang via aw) (aw: rev 3a1f981686835f64df4498f93dae73fde3f2c7a8)

• hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
• hadoop-hdfs-project/hadoop-hdfs/src/site/apt/HdfsPermissionsGuide.apt.vm

SUCCESS: Integrated in Hadoop-Hdfs-trunk #1884 (See https://builds.apache.org/job/Hadoop-Hdfs-trunk/1884/)
HDFS-6664. HDFS permissions guide documentation states incorrect default group mapping class. (Ray Chiang via aw) (aw: rev 3a1f981686835f64df4498f93dae73fde3f2c7a8)

• hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
• hadoop-hdfs-project/hadoop-hdfs/src/site/apt/HdfsPermissionsGuide.apt.vm

FAILURE: Integrated in Hadoop-Mapreduce-trunk #1909 (See https://builds.apache.org/job/Hadoop-Mapreduce-trunk/1909/)
HDFS-6664. HDFS permissions guide documentation states incorrect default group mapping class. (Ray Chiang via aw) (aw: rev 3a1f981686835f64df4498f93dae73fde3f2c7a8)

• hadoop-hdfs-project/hadoop-hdfs/src/site/apt/HdfsPermissionsGuide.apt.vm
• hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

Thanks for committing!