2. Add Slave Nodes

Use the following instructions to manually add a slave node:

On each new slave node, configure the remote repository as described in "Installing ZooKeeper", in Installing HDP Manually.
On each new slave node, install HDFS.
On each new slave node, install compression libraries.
On each new slave node, create the DataNode and YARN NodeManager local directories.
Copy the Hadoop configurations to the new slave nodes and set appropriate permissions.
- Option I: Copy Hadoop config files from an existing slave node.
  - On an existing slave node, make a copy of the current configurations:
    tar zcvf hadoop_conf.tgz /etc/hadoop/conf
  - Copy this file to each of the new nodes:
    rm -rf /etc/hadoop/conf cd / tar zxvf $location_of_copied_conf_tar_file/hadoop_conf.tgz chmod -R 755 /etc/hadoop/confa

On each of the new slave nodes, start the NodeManager:

su -l yarn -c "/usr/hdp/current/hadoop-yarn-nodemanager/sbin/yarn-daemon.sh start nodemanager"

Optional - If you use a HDFS or YARN/ResourceManager .include file in your cluster, add the new slave nodes to the .include file, then run the applicable refreshNodes command.

To add new DataNodes to the dfs.include file:

On the NameNode host machine, edit the /etc/hadoop/conf/dfs.include file and add the list of the new slave node host names (separated by newline character).

	Note
	If no dfs.include file is specified, all DataNodes are considered to be included in the cluster (unless excluded in the dfs.exclude file). The `dfs.hosts` and `dfs.hosts.exlude` properties in `hdfs-site.xml` are used to specify the `dfs.include` and `dfs.exclude` files.

On the NameNode host machine, execute the following command:
```
su -l hdfs -c "hdfs dfsadmin -refreshNodes"
```

To add new NodeManagers to the yarn.include file:

On the ResourceManager host machine, edit the /etc/hadoop/conf/yarn.include file and add the list of the slave node host names (separated by newline character).

	Note
	If no `yarn.include` file is specified, all NodeManagers are considered to be included in the cluster (unless excluded in the `yarn.exclude` file). The `yarn.resourcemanager.nodes.include-path` and `yarn.resourcemanager.nodes.exclude-path` properties in yarn-site.xml are used to specify the `yarn.include` and `yarn.exclude` files.

On the ResourceManager host machine, execute the following command:
```
su -l yarn -c "yarn rmadmin -refreshNodes"
```

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