HDFS-11204. Document the missing options of hdfs zkfc command. Contributed by Yiqun Lin.

(cherry picked from commit 72bff192cd37ff97442e0f8dd477fbc2e58fc12d)
(cherry picked from commit 190b2dca6204e659ed8561c682c4a03f30258298)

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ha/ZKFailoverController.java

@@ -83,8 +83,11 @@ public abstract class ZKFailoverController {
     ZK_AUTH_KEY
   };
   
-  protected static final String USAGE = 
-      "Usage: hdfs zkfc [ -formatZK [-force] [-nonInteractive] ]";
+  protected static final String USAGE =
+      "Usage: hdfs zkfc [ -formatZK [-force] [-nonInteractive] ]\n"
+      + "\t-force: formats the znode if the znode exists.\n"
+      + "\t-nonInteractive: formats the znode aborts if the znode exists,\n"
+      + "\tunless -force option is specified.";
 
   /** Unable to format the parent znode in ZK */
   static final int ERR_CODE_FORMAT_DENIED = 2;

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

@@ -504,7 +504,7 @@ Usage: `hdfs zkfc [-formatZK [-force] [-nonInteractive]]`
 
 | COMMAND\_OPTION | Description |
 |:---- |:---- |
-| `-formatZK` | Format the Zookeeper instance |
+| `-formatZK` | Format the Zookeeper instance. -force: formats the znode if the znode exists. -nonInteractive: formats the znode aborts if the znode exists, unless -force option is specified. |
 | `-h` | Display help |
 
 This comamnd starts a Zookeeper Failover Controller process for use with [HDFS HA with QJM](./HDFSHighAvailabilityWithQJM.html#Administrative_commands).