HDFS-8553. Document hdfs class path options. Contributed by Brahma Reddy Battula.

(cherry picked from commit d2832b3d4243c6c470c774bc33fd13f70b3e7b72)

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -269,6 +269,9 @@ Release 2.8.0 - UNRELEASED
     HDFS-8116. Cleanup uncessary if LOG.isDebugEnabled() from
     RollingWindowManager. (Brahma Reddy Battula via xyao)
 
+    HDFS-8553. Document hdfs class path options.
+    (Brahma Reddy Battula via cnauroth)
+
   OPTIMIZATIONS
 
     HDFS-8026. Trace FSOutputSummer#writeChecksumChunks rather than

hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HDFSCommands.md

@@ -71,9 +71,15 @@ Commands useful for users of a hadoop cluster.
 
 ### `classpath`
 
-Usage: `hdfs classpath`
+Usage: `hdfs classpath [--glob |--jar <path> |-h |--help]`
 
-Prints the class path needed to get the Hadoop jar and the required libraries
+| COMMAND\_OPTION | Description |
+|:---- |:---- |
+| `--glob` | expand wildcards |
+| `--jar` *path* | write classpath as manifest in jar named *path* |
+| `-h`, `--help` | print help |
+
+Prints the class path needed to get the Hadoop jar and the required libraries. If called without arguments, then prints the classpath set up by the command scripts, which is likely to contain wildcards in the classpath entries. Additional options print the classpath after wildcard expansion or write the classpath into the manifest of a jar file. The latter is useful in environments where wildcards cannot be used and the expanded classpath exceeds the maximum supported command line length.
 
 ### `dfs`