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<h1>Commands Manual</h1>
<div id="minitoc-area">
<ul class="minitoc">
<li>
<a href="#Overview">Overview</a>
<ul class="minitoc">
<li>
<a href="#Generic+Options">Generic Options</a>
</li>
</ul>
</li>
<li>
<a href="#User+Commands"> User Commands </a>
<ul class="minitoc">
<li>
<a href="#archive"> archive </a>
</li>
<li>
<a href="#distcp"> distcp </a>
</li>
<li>
<a href="#fs"> fs </a>
</li>
<li>
<a href="#fsck"> fsck </a>
</li>
<li>
<a href="#jar"> jar </a>
</li>
<li>
<a href="#job"> job </a>
</li>
<li>
<a href="#pipes"> pipes </a>
</li>
<li>
<a href="#version"> version </a>
</li>
<li>
<a href="#CLASSNAME"> CLASSNAME </a>
</li>
</ul>
</li>
<li>
<a href="#Administration+Commands"> Administration Commands </a>
<ul class="minitoc">
<li>
<a href="#balancer"> balancer </a>
</li>
<li>
<a href="#daemonlog"> daemonlog </a>
</li>
<li>
<a href="#datanode"> datanode</a>
</li>
<li>
<a href="#dfsadmin"> dfsadmin </a>
</li>
<li>
<a href="#jobtracker"> jobtracker </a>
</li>
<li>
<a href="#namenode"> namenode </a>
</li>
<li>
<a href="#secondarynamenode"> secondarynamenode </a>
</li>
<li>
<a href="#tasktracker"> tasktracker </a>
</li>
</ul>
</li>
</ul>
</div>
		
<a name="N1000D"></a><a name="Overview"></a>
<h2 class="h3">Overview</h2>
<div class="section">
<p>
				All the hadoop commands are invoked by the bin/hadoop script. Running hadoop
				script without any arguments prints the description for all commands.
			</p>
<p>
				
<span class="codefrag">Usage: hadoop [--config confdir] [COMMAND] [GENERIC_OPTIONS] [COMMAND_OPTIONS]</span>
			
</p>
<p>
				Hadoop has an option parsing framework that employs parsing generic options as well as running classes.
			</p>
<table class="ForrestTable" cellspacing="1" cellpadding="4">
			          
<tr>
<th colspan="1" rowspan="1"> COMMAND_OPTION </th><th colspan="1" rowspan="1"> Description </th>
</tr>
			
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">--config confdir</span></td>
			            <td colspan="1" rowspan="1">Overwrites the default Configuration directory. Default is ${HADOOP_HOME}/conf.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">GENERIC_OPTIONS</span></td>
			            <td colspan="1" rowspan="1">The common set of options supported by multiple commands.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">COMMAND</span>
<br>
<span class="codefrag">COMMAND_OPTIONS</span></td>
			            <td colspan="1" rowspan="1">Various commands with their options are described in the following sections. The commands 
			            have been grouped into <a href="commands_manual.html#User+Commands">User Commands</a> 
			            and <a href="commands_manual.html#Administration+Commands">Administration Commands</a>.</td>
			           
</tr>
			     
</table>
<a name="N10061"></a><a name="Generic+Options"></a>
<h3 class="h4">Generic Options</h3>
<p>
				  Following are supported by <a href="commands_manual.html#dfsadmin">dfsadmin</a>, 
				  <a href="commands_manual.html#fs">fs</a>, <a href="commands_manual.html#fsck">fsck</a> and 
				  <a href="commands_manual.html#job">job</a>. 
				  Applications should implement 
				  <a href="api/org/apache/hadoop/util/Tool.html">Tool</a> to support
				  <a href="api/org/apache/hadoop/util/GenericOptionsParser.html">
				  GenericOptions</a>.
				</p>
<table class="ForrestTable" cellspacing="1" cellpadding="4">
			          
<tr>
<th colspan="1" rowspan="1"> GENERIC_OPTION </th><th colspan="1" rowspan="1"> Description </th>
</tr>
			
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-conf &lt;configuration file&gt;</span></td>
			            <td colspan="1" rowspan="1">Specify an application configuration file.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-D &lt;property=value&gt;</span></td>
			            <td colspan="1" rowspan="1">Use value for given property.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-fs &lt;local|namenode:port&gt;</span></td>
			            <td colspan="1" rowspan="1">Specify a namenode.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-jt &lt;local|jobtracker:port&gt;</span></td>
			            <td colspan="1" rowspan="1">Specify a job tracker. Applies only to <a href="commands_manual.html#job">job</a>.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-files &lt;comma separated list of files&gt;</span></td>
			            <td colspan="1" rowspan="1">Specify comma separated files to be copied to the map reduce cluster. 
			            Applies only to <a href="commands_manual.html#job">job</a>.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-libjars &lt;comma seperated list of jars&gt;</span></td>
			            <td colspan="1" rowspan="1">Specify comma separated jar files to include in the classpath. 
			            Applies only to <a href="commands_manual.html#job">job</a>.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-archives &lt;comma separated list of archives&gt;</span></td>
			            <td colspan="1" rowspan="1">Specify comma separated archives to be unarchived on the compute machines. 
			            Applies only to <a href="commands_manual.html#job">job</a>.</td>
			           
</tr>
				
</table>
</div>
		
		
<a name="N10103"></a><a name="User+Commands"></a>
<h2 class="h3"> User Commands </h2>
<div class="section">
<p>Commands useful for users of a hadoop cluster.</p>
<a name="N1010C"></a><a name="archive"></a>
<h3 class="h4"> archive </h3>
<p>
					Creates a hadoop archive. More information can be found at <a href="hadoop_archives.html">Hadoop Archives</a>.
				</p>
<p>
					
<span class="codefrag">Usage: hadoop archive -archiveName NAME &lt;src&gt;* &lt;dest&gt;</span>
				
</p>
<table class="ForrestTable" cellspacing="1" cellpadding="4">
			          
<tr>
<th colspan="1" rowspan="1"> COMMAND_OPTION </th><th colspan="1" rowspan="1"> Description </th>
</tr>
					   
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-archiveName NAME</span></td>
			            <td colspan="1" rowspan="1">Name of the archive to be created.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">src</span></td>
			            <td colspan="1" rowspan="1">Filesystem pathnames which work as usual with regular expressions.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">dest</span></td>
			            <td colspan="1" rowspan="1">Destination directory which would contain the archive.</td>
			           
</tr>
			     
</table>
<a name="N10157"></a><a name="distcp"></a>
<h3 class="h4"> distcp </h3>
<p>
					Copy file or directories recursively. More information can be found at <a href="distcp.html">DistCp Guide</a>.
				</p>
<p>
					
<span class="codefrag">Usage: hadoop distcp &lt;srcurl&gt; &lt;desturl&gt;</span>
				
</p>
<table class="ForrestTable" cellspacing="1" cellpadding="4">
			          
<tr>
<th colspan="1" rowspan="1"> COMMAND_OPTION </th><th colspan="1" rowspan="1"> Description </th>
</tr>
			
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">srcurl</span></td>
			            <td colspan="1" rowspan="1">Source Url</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">desturl</span></td>
			            <td colspan="1" rowspan="1">Destination Url</td>
			           
</tr>
			     
</table>
<a name="N10194"></a><a name="fs"></a>
<h3 class="h4"> fs </h3>
<p>
					
<span class="codefrag">Usage: hadoop fs [</span><a href="commands_manual.html#Generic+Options">GENERIC_OPTIONS</a><span class="codefrag">] 
					[COMMAND_OPTIONS]</span>
				
</p>
<p>
					Runs a generic filesystem user client.
				</p>
<p>
					The various COMMAND_OPTIONS can be found at <a href="hdfs_shell.html">HDFS Shell Guide</a>.
				</p>
<a name="N101B0"></a><a name="fsck"></a>
<h3 class="h4"> fsck </h3>
<p>
					Runs a HDFS filesystem checking utility. See <a href="hdfs_user_guide.html#Fsck">Fsck</a> for more info.
				</p>
<p>
<span class="codefrag">Usage: hadoop fsck [</span><a href="commands_manual.html#Generic+Options">GENERIC_OPTIONS</a><span class="codefrag">] 
				&lt;path&gt; [-move | -delete | -openforwrite] [-files [-blocks 
				[-locations | -racks]]]</span>
</p>
<table class="ForrestTable" cellspacing="1" cellpadding="4">
			          
<tr>
<th colspan="1" rowspan="1"> COMMAND_OPTION </th><th colspan="1" rowspan="1"> Description </th>
</tr>
			          
<tr>
			            
<td colspan="1" rowspan="1"><span class="codefrag">&lt;path&gt;</span></td>
			            <td colspan="1" rowspan="1">Start checking from this path.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-move</span></td>
			            <td colspan="1" rowspan="1">Move corrupted files to /lost+found</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-delete</span></td>
			            <td colspan="1" rowspan="1">Delete corrupted files.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-openforwrite</span></td>
			            <td colspan="1" rowspan="1">Print out files opened for write.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-files</span></td>
			            <td colspan="1" rowspan="1">Print out files being checked.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-blocks</span></td>
			            <td colspan="1" rowspan="1">Print out block report.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-locations</span></td>
			            <td colspan="1" rowspan="1">Print out locations for every block.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-racks</span></td>
			            <td colspan="1" rowspan="1">Print out network topology for data-node locations.</td>
			           
</tr>
					
</table>
<a name="N10244"></a><a name="jar"></a>
<h3 class="h4"> jar </h3>
<p>
					Runs a jar file. Users can bundle their Map Reduce code in a jar file and execute it using this command.
				</p>
<p>
					
<span class="codefrag">Usage: hadoop jar &lt;jar&gt; [mainClass] args...</span>
				
</p>
<p>
					The streaming jobs are run via this command. Examples can be referred from 
					<a href="streaming.html#More+usage+examples">Streaming examples</a>
				
</p>
<p>
					Word count example is also run using jar command. It can be referred from
					<a href="mapred_tutorial.html#Usage">Wordcount example</a>
				
</p>
<a name="N10262"></a><a name="job"></a>
<h3 class="h4"> job </h3>
<p>
					Command to interact with Map Reduce Jobs.
				</p>
<p>
					
<span class="codefrag">Usage: hadoop job [</span><a href="commands_manual.html#Generic+Options">GENERIC_OPTIONS</a><span class="codefrag">] 
					[-submit &lt;job-file&gt;] | [-status &lt;job-id&gt;] | 
					[-counter &lt;job-id&gt; &lt;group-name&gt; &lt;counter-name&gt;] | [-kill &lt;job-id&gt;] | 
					[-events &lt;job-id&gt; &lt;from-event-#&gt; &lt;#-of-events&gt;] | [-history [all] &lt;jobOutputDir&gt;] |
					[-list [all]] | [-kill-task &lt;task-id&gt;] | [-fail-task &lt;task-id&gt;]</span>
				
</p>
<table class="ForrestTable" cellspacing="1" cellpadding="4">
			          
<tr>
<th colspan="1" rowspan="1"> COMMAND_OPTION </th><th colspan="1" rowspan="1"> Description </th>
</tr>
			
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-submit &lt;job-file&gt;</span></td>
			            <td colspan="1" rowspan="1">Submits the job.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-status &lt;job-id&gt;</span></td>
			            <td colspan="1" rowspan="1">Prints the map and reduce completion percentage and all job counters.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-counter &lt;job-id&gt; &lt;group-name&gt; &lt;counter-name&gt;</span></td>
			            <td colspan="1" rowspan="1">Prints the counter value.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-kill &lt;job-id&gt;</span></td>
			            <td colspan="1" rowspan="1">Kills the job.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-events &lt;job-id&gt; &lt;from-event-#&gt; &lt;#-of-events&gt;</span></td>
			            <td colspan="1" rowspan="1">Prints the events' details received by jobtracker for the given range.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-history [all] &lt;jobOutputDir&gt;</span></td>
			            <td colspan="1" rowspan="1">-history &lt;jobOutputDir&gt; prints job details, failed and killed tip details. More details 
			            about the job such as successful tasks and task attempts made for each task can be viewed by 
			            specifying the [all] option. </td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-list [all]</span></td>
			            <td colspan="1" rowspan="1">-list all displays all jobs. -list displays only jobs which are yet to complete.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-kill-task &lt;task-id&gt;</span></td>
			            <td colspan="1" rowspan="1">Kills the task. Killed tasks are NOT counted against failed attempts.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-fail-task &lt;task-id&gt;</span></td>
			            <td colspan="1" rowspan="1">Fails the task. Failed tasks are counted against failed attempts.</td>
			           
</tr>
					
</table>
<a name="N10302"></a><a name="pipes"></a>
<h3 class="h4"> pipes </h3>
<p>
					Runs a pipes job.
				</p>
<p>
					
<span class="codefrag">Usage: hadoop pipes [-conf &lt;path&gt;] [-jobconf &lt;key=value&gt;, &lt;key=value&gt;, ...] 
					[-input &lt;path&gt;] [-output &lt;path&gt;] [-jar &lt;jar file&gt;] [-inputformat &lt;class&gt;] 
					[-map &lt;class&gt;] [-partitioner &lt;class&gt;] [-reduce &lt;class&gt;] [-writer &lt;class&gt;] 
					[-program &lt;executable&gt;] [-reduces &lt;num&gt;] </span>
				
</p>
<table class="ForrestTable" cellspacing="1" cellpadding="4">
			          
<tr>
<th colspan="1" rowspan="1"> COMMAND_OPTION </th><th colspan="1" rowspan="1"> Description </th>
</tr>
			
			          
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-conf &lt;path&gt;</span></td>
			            <td colspan="1" rowspan="1">Configuration for job</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-jobconf &lt;key=value&gt;, &lt;key=value&gt;, ...</span></td>
			            <td colspan="1" rowspan="1">Add/override configuration for job</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-input &lt;path&gt;</span></td>
			            <td colspan="1" rowspan="1">Input directory</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-output &lt;path&gt;</span></td>
			            <td colspan="1" rowspan="1">Output directory</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-jar &lt;jar file&gt;</span></td>
			            <td colspan="1" rowspan="1">Jar filename</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-inputformat &lt;class&gt;</span></td>
			            <td colspan="1" rowspan="1">InputFormat class</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-map &lt;class&gt;</span></td>
			            <td colspan="1" rowspan="1">Java Map class</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-partitioner &lt;class&gt;</span></td>
			            <td colspan="1" rowspan="1">Java Partitioner</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-reduce &lt;class&gt;</span></td>
			            <td colspan="1" rowspan="1">Java Reduce class</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-writer &lt;class&gt;</span></td>
			            <td colspan="1" rowspan="1">Java RecordWriter</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-program &lt;executable&gt;</span></td>
			            <td colspan="1" rowspan="1">Executable URI</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-reduces &lt;num&gt;</span></td>
			            <td colspan="1" rowspan="1">Number of reduces</td>
			           
</tr>
					
</table>
<a name="N103C7"></a><a name="version"></a>
<h3 class="h4"> version </h3>
<p>
					Prints the version.
				</p>
<p>
					
<span class="codefrag">Usage: hadoop version</span>
				
</p>
<a name="N103D7"></a><a name="CLASSNAME"></a>
<h3 class="h4"> CLASSNAME </h3>
<p>
					 hadoop script can be used to invoke any class.
				</p>
<p>
					
<span class="codefrag">Usage: hadoop CLASSNAME</span>
				
</p>
<p>
					 Runs the class named CLASSNAME.
				</p>
</div>
		
		
<a name="N103EB"></a><a name="Administration+Commands"></a>
<h2 class="h3"> Administration Commands </h2>
<div class="section">
<p>Commands useful for administrators of a hadoop cluster.</p>
<a name="N103F4"></a><a name="balancer"></a>
<h3 class="h4"> balancer </h3>
<p>
					Runs a cluster balancing utility. An administrator can simply press Ctrl-C to stop the 
					rebalancing process. See <a href="hdfs_user_guide.html#Rebalancer">Rebalancer</a> for more details.
				</p>
<p>
					
<span class="codefrag">Usage: hadoop balancer [-threshold &lt;threshold&gt;]</span>
				
</p>
<table class="ForrestTable" cellspacing="1" cellpadding="4">
			          
<tr>
<th colspan="1" rowspan="1"> COMMAND_OPTION </th><th colspan="1" rowspan="1"> Description </th>
</tr>
			
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-threshold &lt;threshold&gt;</span></td>
			            <td colspan="1" rowspan="1">Percentage of disk capacity. This overwrites the default threshold.</td>
			           
</tr>
			     
</table>
<a name="N10423"></a><a name="daemonlog"></a>
<h3 class="h4"> daemonlog </h3>
<p>
					 Get/Set the log level for each daemon.
				</p>
<p>
					
<span class="codefrag">Usage: hadoop daemonlog  -getlevel &lt;host:port&gt; &lt;name&gt;</span>
<br>
					
<span class="codefrag">Usage: hadoop daemonlog  -setlevel &lt;host:port&gt; &lt;name&gt; &lt;level&gt;</span>
				
</p>
<table class="ForrestTable" cellspacing="1" cellpadding="4">
			          
<tr>
<th colspan="1" rowspan="1"> COMMAND_OPTION </th><th colspan="1" rowspan="1"> Description </th>
</tr>
			
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-getlevel &lt;host:port&gt; &lt;name&gt;</span></td>
			            <td colspan="1" rowspan="1">Prints the log level of the daemon running at &lt;host:port&gt;. 
			            This command internally connects to http://&lt;host:port&gt;/logLevel?log=&lt;name&gt;</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-setlevel &lt;host:port&gt; &lt;name&gt; &lt;level&gt;</span></td>
			            <td colspan="1" rowspan="1">Sets the log level of the daemon running at &lt;host:port&gt;. 
			            This command internally connects to http://&lt;host:port&gt;/logLevel?log=&lt;name&gt;</td>
			           
</tr>
			     
</table>
<a name="N10460"></a><a name="datanode"></a>
<h3 class="h4"> datanode</h3>
<p>
					Runs a HDFS datanode.
				</p>
<p>
					
<span class="codefrag">Usage: hadoop datanode [-rollback]</span>
				
</p>
<table class="ForrestTable" cellspacing="1" cellpadding="4">
			          
<tr>
<th colspan="1" rowspan="1"> COMMAND_OPTION </th><th colspan="1" rowspan="1"> Description </th>
</tr>
			
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-rollback</span></td>
			            <td colspan="1" rowspan="1">Rollsback the datanode to the previous version. This should be used after stopping the datanode 
			            and distributing the old hadoop version.</td>
			           
</tr>
			     
</table>
<a name="N1048B"></a><a name="dfsadmin"></a>
<h3 class="h4"> dfsadmin </h3>
<p>
					Runs a HDFS dfsadmin client.
				</p>
<p>
					
<span class="codefrag">Usage: hadoop dfsadmin  [</span><a href="commands_manual.html#Generic+Options">GENERIC_OPTIONS</a><span class="codefrag">] [-report] [-safemode enter | leave | get | wait] [-refreshNodes]
					 [-finalizeUpgrade] [-upgradeProgress status | details | force] [-metasave filename] 
					 [-setQuota &lt;quota&gt; &lt;dirname&gt;...&lt;dirname&gt;] [-clrQuota &lt;dirname&gt;...&lt;dirname&gt;] 
					 [-help [cmd]]</span>
				
</p>
<table class="ForrestTable" cellspacing="1" cellpadding="4">
			          
<tr>
<th colspan="1" rowspan="1"> COMMAND_OPTION </th><th colspan="1" rowspan="1"> Description </th>
</tr>
			
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-report</span></td>
			            <td colspan="1" rowspan="1">Reports basic filesystem information and statistics.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-safemode enter | leave | get | wait</span></td>
			            <td colspan="1" rowspan="1">Safe mode maintenance command.
                Safe mode is a Namenode state in which it <br>
                        1.  does not accept changes to the name space (read-only) <br> 
                        2.  does not replicate or delete blocks. <br>
                Safe mode is entered automatically at Namenode startup, and
                leaves safe mode automatically when the configured minimum
                percentage of blocks satisfies the minimum replication
                condition.  Safe mode can also be entered manually, but then
                it can only be turned off manually as well.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-refreshNodes</span></td>
			            <td colspan="1" rowspan="1">Re-read the hosts and exclude files to update the set
                of Datanodes that are allowed to connect to the Namenode
                and those that should be decommissioned or recommissioned.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-finalizeUpgrade</span></td>
			            <td colspan="1" rowspan="1">Finalize upgrade of HDFS.
                Datanodes delete their previous version working directories,
                followed by Namenode doing the same.
                This completes the upgrade process.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-upgradeProgress status | details | force</span></td>
			            <td colspan="1" rowspan="1">Request current distributed upgrade status,
                a detailed status or force the upgrade to proceed.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-metasave filename</span></td>
			            <td colspan="1" rowspan="1">Save Namenode's primary data structures
                to &lt;filename&gt; in the directory specified by hadoop.log.dir property.
                &lt;filename&gt; will contain one line for each of the following <br>
                        1. Datanodes heart beating with Namenode<br>
                        2. Blocks waiting to be replicated<br>
                        3. Blocks currrently being replicated<br>
                        4. Blocks waiting to be deleted</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-setQuota &lt;quota&gt; &lt;dirname&gt;...&lt;dirname&gt;</span></td>
			            <td colspan="1" rowspan="1">Set the quota &lt;quota&gt; for each directory &lt;dirname&gt;.
                The directory quota is a long integer that puts a hard limit on the number of names in the directory tree.<br>
                Best effort for the directory, with faults reported if<br>
                1. N is not a positive integer, or<br>
                2. user is not an administrator, or<br>
                3. the directory does not exist or is a file, or<br>
                4. the directory would immediately exceed the new quota.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-clrQuota &lt;dirname&gt;...&lt;dirname&gt;</span></td>
			            <td colspan="1" rowspan="1">Clear the quota for each directory &lt;dirname&gt;.<br>
                Best effort for the directory. with fault reported if<br>
                1. the directory does not exist or is a file, or<br>
                2. user is not an administrator.<br>
                It does not fault if the directory has no quota.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-help [cmd]</span></td>
			            <td colspan="1" rowspan="1"> Displays help for the given command or all commands if none
                is specified.</td>
			           
</tr>
			     
</table>
<a name="N1054B"></a><a name="jobtracker"></a>
<h3 class="h4"> jobtracker </h3>
<p>
					Runs the MapReduce job Tracker node.
				</p>
<p>
					
<span class="codefrag">Usage: hadoop jobtracker</span>
				
</p>
<a name="N1055B"></a><a name="namenode"></a>
<h3 class="h4"> namenode </h3>
<p>
					Runs the namenode. More info about the upgrade, rollback and finalize is at 
					<a href="hdfs_user_guide.html#Upgrade+and+Rollback">Upgrade Rollback</a>
				
</p>
<p>
					
<span class="codefrag">Usage: hadoop namenode [-format] | [-upgrade] | [-rollback] | [-finalize] | [-importCheckpoint]</span>
				
</p>
<table class="ForrestTable" cellspacing="1" cellpadding="4">
			          
<tr>
<th colspan="1" rowspan="1"> COMMAND_OPTION </th><th colspan="1" rowspan="1"> Description </th>
</tr>
			
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-format</span></td>
			            <td colspan="1" rowspan="1">Formats the namenode. It starts the namenode, formats it and then shut it down.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-upgrade</span></td>
			            <td colspan="1" rowspan="1">Namenode should be started with upgrade option after the distribution of new hadoop version.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-rollback</span></td>
			            <td colspan="1" rowspan="1">Rollsback the namenode to the previous version. This should be used after stopping the cluster 
			            and distributing the old hadoop version.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-finalize</span></td>
			            <td colspan="1" rowspan="1">Finalize will remove the previous state of the files system. Recent upgrade will become permanent. 
			            Rollback option will not be available anymore. After finalization it shuts the namenode down.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-importCheckpoint</span></td>
			            <td colspan="1" rowspan="1">Loads image from a checkpoint directory and save it into the current one. Checkpoint dir 
			            is read from property fs.checkpoint.dir</td>
			           
</tr>
			     
</table>
<a name="N105C2"></a><a name="secondarynamenode"></a>
<h3 class="h4"> secondarynamenode </h3>
<p>
					Runs the HDFS secondary namenode. See <a href="hdfs_user_guide.html#Secondary+Namenode">Secondary Namenode</a> 
					for more info.
				</p>
<p>
					
<span class="codefrag">Usage: hadoop secondarynamenode [-checkpoint [force]] | [-geteditsize]</span>
				
</p>
<table class="ForrestTable" cellspacing="1" cellpadding="4">
			          
<tr>
<th colspan="1" rowspan="1"> COMMAND_OPTION </th><th colspan="1" rowspan="1"> Description </th>
</tr>
			
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-checkpoint [force]</span></td>
			            <td colspan="1" rowspan="1">Checkpoints the Secondary namenode if EditLog size &gt;= fs.checkpoint.size. 
			            If -force is used, checkpoint irrespective of EditLog size.</td>
			           
</tr>
			           
<tr>
			          	
<td colspan="1" rowspan="1"><span class="codefrag">-geteditsize</span></td>
			            <td colspan="1" rowspan="1">Prints the EditLog size.</td>
			           
</tr>
			     
</table>
<a name="N105FF"></a><a name="tasktracker"></a>
<h3 class="h4"> tasktracker </h3>
<p>
					Runs a MapReduce task Tracker node.
				</p>
<p>
					
<span class="codefrag">Usage: hadoop tasktracker</span>
				
</p>
</div>
		
		
		      

	
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