3. Configure YARN and MapReduce

After you install Hadoop, modify your configs.

Upload the MapReduce tarball to HDFS. As the HDFS user, for example 'hdfs':

su $HDFS_USER
hdfs dfs -mkdir -p /hdp/apps/<hdp_version>/mapreduce/
hdfs dfs -put /usr/hdp/current/hadoop-client/mapreduce.tar.gz /hdp/apps/<hdp_version>/mapreduce/
hdfs dfs -chown -R hdfs:hadoop /hdp
hdfs dfs -chmod -R 555 /hdp/apps/<hdp_version>/mapreduce
hdfs dfs -chmod -R 444 /hdp/apps/<hdp_version>/mapreduce/mapreduce.tar.gz

Where $HDFS_USER is the HDFS user, for example hdfs, and <hdp_version> is the current HDP version, for example 2.2.4.2.

Copy mapred-site.xml from the companion files and make the following changes to mapred-site.xml:

Add:

<property>
     <name>mapreduce.admin.map.child.java.opts</name>
     <value>-server -Djava.net.preferIPv4Stack=true -Dhdp.version=${hdp.version}</value>
     <final>true</final>
</property>

	Note
	You do not need to modify ${hdp.version}.

Modify the following existing properties to include ${hdp.version}:

 <property>
     <name>mapreduce.admin.user.env</name> 
     <value>LD_LIBRARY_PATH=/usr/hdp/${hdp.version}/hadoop/lib/native:/usr/hdp/${hdp.version}/hadoop/lib/native/Linux-amd64-64</value>
</property>

<property>
     <name>mapreduce.application.framework.path</name>
     <value>/hdp/apps/${hdp.version}/mapreduce/mapreduce.tar.gz#mr-framework</value>
</property>

<property>
     <name>mapreduce.application.classpath</name>
     <value>$PWD/mr-framework/hadoop/share/hadoop/mapreduce/*:$PWD/mr-framework/hadoop/share/hadoop/mapreduce/lib/*:$PWD/mr-framework/hadoop/share/hadoop/common/*:$PWD/mr-framework/hadoop/share/hadoop/common/lib/*:$PWD/mr-framework/hadoop/share/hadoop/yarn/*:$PWD/mr-framework/hadoop/share/hadoop/yarn/lib/*:$PWD/mr-framework/hadoop/share/hadoop/hdfs/*:$PWD/mr-framework/hadoop/share/hadoop/hdfs/lib/*:/usr/hdp/${hdp.version}/hadoop/lib/hadoop-lzo-0.6.0.${hdp.version}.jar:/etc/hadoop/conf/secure</value>
</property>

	Note
	You do not need to modify ${hdp.version}.

Copy yarn-site.xml from the companion files and modify:

<property>
     <name>yarn.application.classpath</name> 
     <value>$HADOOP_CONF_DIR,/usr/hdp/${hdp.version}/hadoop-client/*,/usr/hdp/${hdp.version}/hadoop-client/lib/*,/usr/hdp/${hdp.version}/hadoop-hdfs-client/*,/usr/hdp/${hdp.version}/hadoop-hdfs-client/lib/*,/usr/hdp/${hdp.version}/hadoop-yarn-client/*,/usr/hdp/${hdp.version}/hadoop-yarn-client/lib/*</value>
</property>

For secure clusters, you must create and configure the container-executor.cfg configuration file:
- Create the container-executor.cfg file in /etc/hadoop/conf/.
- Insert the following properties:
```
yarn.nodemanager.linux-container-executor.group=hadoop
banned.users=hdfs,yarn,mapred
min.user.id=1000
```
- Set the file /etc/hadoop/conf/container-executor.cfg file permissions to only be readable by root:
```
chown root:hadoop /etc/hadoop/conf/container-executor.cfg
chmod 400 /etc/hadoop/conf/container-executor.cfg
```
- Set the container-executor program so that only root or hadoop group users can execute it:
```
chown root:hadoop /usr/hdp/${hdp.version}/hadoop-yarn/bin/container-executor
chmod 6050 /usr/hdp/${hdp.version}/hadoop-yarn/bin/container-executor
```

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