Operating the Hadoop Cluster

 

Operating the Hadoop Cluster

Once all the necessary configuration is complete, distribute the files to the HADOOP_CONF_DIR directory on all the machines. This should be the same directory on all machines.

In general, it is recommended that HDFS and YARN run as separate users. In the majority of installations, HDFS processes execute as ‘hdfs’. YARN is typically using the ‘yarn’ account.

Hadoop Startup

To start a Hadoop cluster you will need to start both the HDFS and YARN cluster.

The first time you bring up HDFS, it must be formatted. Format a new distributed filesystem as hdfs:

[hdfs]$ $HADOOP_HOME/bin/hdfs namenode -format

Start the HDFS NameNode with the following command on the designated node as hdfs:

[hdfs]$ $HADOOP_HOME/bin/hdfs --daemon start namenode

Start a HDFS DataNode with the following command on each designated node as hdfs:

[hdfs]$ $HADOOP_HOME/bin/hdfs --daemon start datanode

If etc/hadoop/workers and ssh trusted access is configured , all of the HDFS processes can be started with a utility script. As hdfs:

[hdfs]$ $HADOOP_HOME/sbin/start-dfs.sh

Start the YARN with the following command, run on the designated ResourceManager as yarn:

[yarn]$ $HADOOP_HOME/bin/yarn --daemon start resourcemanager

Run a script to start a NodeManager on each designated host as yarn:

[yarn]$ $HADOOP_HOME/bin/yarn --daemon start nodemanager

Start a standalone WebAppProxy server. Run on the WebAppProxy server as yarn. If multiple servers are used with load balancing it should be run on each of them:

[yarn]$ $HADOOP_HOME/bin/yarn --daemon start proxyserver

If etc/hadoop/workers and ssh trusted access is configured , all of the YARN processes can be started with a utility script. As yarn:

[yarn]$ $HADOOP_HOME/sbin/start-yarn.sh

Start the MapReduce JobHistory Server with the following command, run on the designated server as mapred:

[mapred]$ $HADOOP_HOME/bin/mapred --daemon start historyserver 

 

 

 

 

 

Hadoop Shutdown

Stop the NameNode with the following command, run on the designated NameNode as hdfs:

[hdfs]$ $HADOOP_HOME/bin/hdfs --daemon stop namenode

Run a script to stop a DataNode as hdfs:

[hdfs]$ $HADOOP_HOME/bin/hdfs --daemon stop datanode

If etc/hadoop/workers and ssh trusted access is configured, all of the HDFS processes may be stopped with a utility script. As hdfs:

[hdfs]$ $HADOOP_HOME/sbin/stop-dfs.sh

Stop the ResourceManager with the following command, run on the designated ResourceManager as yarn:

[yarn]$ $HADOOP_HOME/bin/yarn --daemon stop resourcemanager

Run a script to stop a NodeManager on a worker as yarn:

[yarn]$ $HADOOP_HOME/bin/yarn --daemon stop nodemanager

If etc/hadoop/workers and ssh trusted access is configured , all of the YARN processes can be stopped with a utility script. As yarn:

[yarn]$ $HADOOP_HOME/sbin/stop-yarn.sh

Stop the WebAppProxy server. Run on the WebAppProxy server as yarn. If multiple servers are used with load balancing it should be run on each of them:

[yarn]$ $HADOOP_HOME/bin/yarn stop proxyserver

Stop the MapReduce JobHistory Server with the following command, run on the designated server as mapred:

[mapred]$ $HADOOP_HOME/bin/mapred --daemon stop historyserver

 

Web Interfaces

Once the Hadoop cluster is up and running check the web-ui of the components as described below:

Daemon	Web Interface	Notes
NameNode	http://nn_host:port/	Default HTTP port is 9870.
ResourceManager	http://rm_host:port/	Default HTTP port is 8088.
MapReduce JobHistory Server	http://jhs_host:port/	Default HTTP port is 19888.

 

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