diff --git a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
index bc333e6e9d..7586f950a5 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
+++ b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
@@ -192,6 +192,8 @@ Trunk (Unreleased)
 
     HDFS-5450. Better API for getting the cached blocks locations. (wang)
 
+    HDFS-5485. Add command-line support for modifyDirective. (cmccabe)
+
   OPTIMIZATIONS
     HDFS-5349. DNA_CACHE and DNA_UNCACHE should be by blockId only. (cmccabe)
 
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/CacheAdmin.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/CacheAdmin.java
index 6ae902208d..5352d669e7 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/CacheAdmin.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/CacheAdmin.java
@@ -248,6 +248,84 @@ public int run(Configuration conf, List<String> args) throws IOException {
     }
   }
 
+  private static class ModifyPathBasedCacheDirectiveCommand implements Command {
+    @Override
+    public String getName() {
+      return "-modifyDirective";
+    }
+
+    @Override
+    public String getShortUsage() {
+      return "[" + getName() +
+          " -id <id> [-path <path>] [-replication <replication>] " +
+          "[-pool <pool-name>] ]\n";
+    }
+
+    @Override
+    public String getLongUsage() {
+      TableListing listing = getOptionDescriptionListing();
+      listing.addRow("<id>", "The ID of the directive to modify (required)");
+      listing.addRow("<path>", "A path to cache. The path can be " +
+          "a directory or a file. (optional)");
+      listing.addRow("<replication>", "The cache replication factor to use. " +
+          "(optional)");
+      listing.addRow("<pool-name>", "The pool to which the directive will be " +
+          "added. You must have write permission on the cache pool "
+          + "in order to move a directive into it. (optional)");
+      return getShortUsage() + "\n" +
+        "Modify a PathBasedCache directive.\n\n" +
+        listing.toString();
+    }
+
+    @Override
+    public int run(Configuration conf, List<String> args) throws IOException {
+      PathBasedCacheDirective.Builder builder =
+        new PathBasedCacheDirective.Builder();
+      boolean modified = false;
+      String idString = StringUtils.popOptionWithArgument("-id", args);
+      if (idString == null) {
+        System.err.println("You must specify a directive ID with -id.");
+        return 1;
+      }
+      builder.setId(Long.parseLong(idString));
+      String path = StringUtils.popOptionWithArgument("-path", args);
+      if (path != null) {
+        builder.setPath(new Path(path));
+        modified = true;
+      }
+      String replicationString =
+        StringUtils.popOptionWithArgument("-replication", args);
+      if (replicationString != null) {
+        builder.setReplication(Short.parseShort(replicationString));
+        modified = true;
+      }
+      String poolName =
+        StringUtils.popOptionWithArgument("-pool", args);
+      if (poolName != null) {
+        builder.setPool(poolName);
+        modified = true;
+      }
+      if (!args.isEmpty()) {
+        System.err.println("Can't understand argument: " + args.get(0));
+        System.err.println("Usage is " + getShortUsage());
+        return 1;
+      }
+      if (!modified) {
+        System.err.println("No modifications were specified.");
+        return 1;
+      }
+      DistributedFileSystem dfs = getDFS(conf);
+      try {
+        dfs.modifyPathBasedCacheDirective(builder.build());
+        System.out.println("Modified PathBasedCache entry " + idString);
+      } catch (IOException e) {
+        System.err.println(prettifyException(e));
+        return 2;
+      }
+      return 0;
+    }
+  }
+
   private static class RemovePathBasedCacheDirectivesCommand implements Command {
     @Override
     public String getName() {
@@ -352,6 +430,7 @@ public int run(Configuration conf, List<String> args) throws IOException {
       TableListing tableListing = new TableListing.Builder().
           addField("ID", Justification.LEFT).
           addField("POOL", Justification.LEFT).
+          addField("REPLICATION", Justification.LEFT).
           addField("PATH", Justification.LEFT).
           build();
       DistributedFileSystem dfs = getDFS(conf);
@@ -362,6 +441,7 @@ public int run(Configuration conf, List<String> args) throws IOException {
         PathBasedCacheDirective directive = iter.next();
         String row[] = new String[] {
             "" + directive.getId(), directive.getPool(),
+            "" + directive.getReplication(),
             directive.getPath().toUri().getPath(),
         };
         tableListing.addRow(row);
@@ -744,9 +824,10 @@ public int run(Configuration conf, List<String> args) throws IOException {
 
   private static Command[] COMMANDS = {
     new AddPathBasedCacheDirectiveCommand(),
+    new ModifyPathBasedCacheDirectiveCommand(),
+    new ListPathBasedCacheDirectiveCommand(),
     new RemovePathBasedCacheDirectiveCommand(),
     new RemovePathBasedCacheDirectivesCommand(),
-    new ListPathBasedCacheDirectiveCommand(),
     new AddCachePoolCommand(),
     new ModifyCachePoolCommand(),
     new RemoveCachePoolCommand(),
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/resources/testCacheAdminConf.xml b/hadoop-hdfs-project/hadoop-hdfs/src/test/resources/testCacheAdminConf.xml
index 54dd7a97b7..eba62ba1fe 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/resources/testCacheAdminConf.xml
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/resources/testCacheAdminConf.xml
@@ -180,15 +180,15 @@
         </comparator>
         <comparator>
           <type>SubstringComparator</type>
-          <expected-output>1   pool1  /foo</expected-output>
+          <expected-output>1   pool1  1            /foo</expected-output>
         </comparator>
         <comparator>
           <type>SubstringComparator</type>
-          <expected-output>2   pool1  /bar</expected-output>
+          <expected-output>2   pool1  1            /bar</expected-output>
         </comparator>
         <comparator>
           <type>SubstringComparator</type>
-          <expected-output>3   pool1  /baz</expected-output>
+          <expected-output>3   pool1  2            /baz</expected-output>
         </comparator>
       </comparators>
     </test>
@@ -234,11 +234,11 @@
         </comparator>
         <comparator>
           <type>SubstringComparator</type>
-          <expected-output>8   pool2  /baz</expected-output>
+          <expected-output>8   pool2  1            /baz</expected-output>
         </comparator>
         <comparator>
           <type>SubstringComparator</type>
-          <expected-output>9   pool2  /buz</expected-output>
+          <expected-output>9   pool2  1            /buz</expected-output>
         </comparator>
       </comparators>
     </test>
@@ -265,11 +265,11 @@
         </comparator>
         <comparator>
           <type>SubstringComparator</type>
-          <expected-output>10  pool1  /foo</expected-output>
+          <expected-output>10  pool1  1            /foo</expected-output>
         </comparator>
         <comparator>
           <type>SubstringComparator</type>
-          <expected-output>12  pool2  /foo</expected-output>
+          <expected-output>12  pool2  1            /foo</expected-output>
         </comparator>
       </comparators>
     </test>
@@ -296,7 +296,7 @@
         </comparator>
         <comparator>
           <type>SubstringComparator</type>
-          <expected-output>16  pool2  /foo</expected-output>
+          <expected-output>16  pool2  1            /foo</expected-output>
         </comparator>
       </comparators>
     </test>
@@ -320,7 +320,7 @@
         </comparator>
         <comparator>
           <type>SubstringComparator</type>
-          <expected-output>19  pool1  /bar</expected-output>
+          <expected-output>19  pool1  1            /bar</expected-output>
         </comparator>
       </comparators>
     </test>
@@ -349,11 +349,37 @@
         </comparator>
         <comparator>
           <type>SubstringComparator</type>
-          <expected-output>22  pool1  /bar</expected-output>
+          <expected-output>22  pool1  1            /bar</expected-output>
         </comparator>
         <comparator>
           <type>SubstringComparator</type>
-          <expected-output>24  pool2  /bar</expected-output>
+          <expected-output>24  pool2  1            /bar</expected-output>
+        </comparator>
+      </comparators>
+    </test>
+
+    <test> <!--Tested -->
+      <description>Testing modifying directives</description>
+      <test-commands>
+        <cache-admin-command>-addPool pool1</cache-admin-command>
+        <cache-admin-command>-addPool pool2</cache-admin-command>
+        <cache-admin-command>-addDirective -path /foo -pool pool2</cache-admin-command>
+        <cache-admin-command>-modifyDirective -id 25 -path /bar2</cache-admin-command>
+        <cache-admin-command>-modifyDirective -id 25 -pool pool1 -path /bar3</cache-admin-command>
+        <cache-admin-command>-listDirectives -path /bar3</cache-admin-command>
+      </test-commands>
+      <cleanup-commands>
+        <cache-admin-command>-removePool pool1</cache-admin-command>
+        <cache-admin-command>-removePool pool2</cache-admin-command>
+      </cleanup-commands>
+      <comparators>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>Found 1 entry</expected-output>
+        </comparator>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>25  pool1  1            /bar3</expected-output>
         </comparator>
       </comparators>
     </test>