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  ---
  Hadoop Map Reduce Next Generation-${project.version} - Cluster Setup
  ---
  ---
  ${maven.build.timestamp}

%{toc|section=1|fromDepth=0}

Hadoop MapReduce Next Generation - Cluster Setup

* {Purpose}

  This document describes how to install, configure and manage non-trivial
  Hadoop clusters ranging from a few nodes to extremely large clusters
  with thousands of nodes.

  To play with Hadoop, you may first want to install it on a single
  machine (see {{{./SingleCluster.html}Single Node Setup}}).

* {Prerequisites}

  Download a stable version of Hadoop from Apache mirrors.

* {Installation}

  Installing a Hadoop cluster typically involves unpacking the software on all
  the machines in the cluster or installing RPMs.

  Typically one machine in the cluster is designated as the NameNode and
  another machine the as ResourceManager, exclusively. These are the masters.

  The rest of the machines in the cluster act as both DataNode and NodeManager.
  These are the slaves.

* {Running Hadoop in Non-Secure Mode}

  The following sections describe how to configure a Hadoop cluster.

  {Configuration Files}

    Hadoop configuration is driven by two types of important configuration files:

      * Read-only default configuration - <<<core-default.xml>>>,
        <<<hdfs-default.xml>>>, <<<yarn-default.xml>>> and
        <<<mapred-default.xml>>>.

      * Site-specific configuration - <<conf/core-site.xml>>,
        <<conf/hdfs-site.xml>>, <<conf/yarn-site.xml>> and
        <<conf/mapred-site.xml>>.


    Additionally, you can control the Hadoop scripts found in the bin/
    directory of the distribution, by setting site-specific values via the
    <<conf/hadoop-env.sh>> and <<yarn-env.sh>>.

  {Site Configuration}

  To configure the Hadoop cluster you will need to configure the
  <<<environment>>> in which the Hadoop daemons execute as well as the
  <<<configuration parameters>>> for the Hadoop daemons.

  The Hadoop daemons are NameNode/DataNode and ResourceManager/NodeManager.


** {Configuring Environment of Hadoop Daemons}

  Administrators should use the <<conf/hadoop-env.sh>> and
  <<conf/yarn-env.sh>> script to do site-specific customization of the
  Hadoop daemons' process environment.

  At the very least you should specify the <<<JAVA_HOME>>> so that it is
  correctly defined on each remote node.

  In most cases you should also specify <<<HADOOP_PID_DIR>>> and
  <<<HADOOP_SECURE_DN_PID_DIR>>> to point to directories that can only be
  written to by the users that are going to run the hadoop daemons.
  Otherwise there is the potential for a symlink attack.

  Administrators can configure individual daemons using the configuration
  options shown below in the table:

*--------------------------------------+--------------------------------------+
|| Daemon                              || Environment Variable                |
*--------------------------------------+--------------------------------------+
| NameNode                             | HADOOP_NAMENODE_OPTS                 |
*--------------------------------------+--------------------------------------+
| DataNode                             | HADOOP_DATANODE_OPTS                 |
*--------------------------------------+--------------------------------------+
| Secondary NameNode                   | HADOOP_SECONDARYNAMENODE_OPTS        |
*--------------------------------------+--------------------------------------+
| ResourceManager                      | YARN_RESOURCEMANAGER_OPTS            |
*--------------------------------------+--------------------------------------+
| NodeManager                          | YARN_NODEMANAGER_OPTS                |
*--------------------------------------+--------------------------------------+
| WebAppProxy                          | YARN_PROXYSERVER_OPTS                |
*--------------------------------------+--------------------------------------+
| Map Reduce Job History Server        | HADOOP_JOB_HISTORYSERVER_OPTS        |
*--------------------------------------+--------------------------------------+


  For example, To configure Namenode to use parallelGC, the following
  statement should be added in hadoop-env.sh :

----
  export HADOOP_NAMENODE_OPTS="-XX:+UseParallelGC ${HADOOP_NAMENODE_OPTS}"
----

  Other useful configuration parameters that you can customize include:

    * <<<HADOOP_LOG_DIR>>> / <<<YARN_LOG_DIR>>> - The directory where the
      daemons' log files are stored. They are automatically created if they
      don't exist.

    * <<<HADOOP_HEAPSIZE>>> / <<<YARN_HEAPSIZE>>> - The maximum amount of
      heapsize to use, in MB e.g. if the varibale is set to 1000 the heap
      will be set to 1000MB.  This is used to configure the heap
      size for the daemon. By default, the value is 1000.  If you want to
      configure the values separately for each deamon you can use.

*--------------------------------------+--------------------------------------+
|| Daemon                              || Environment Variable                |
*--------------------------------------+--------------------------------------+
| ResourceManager                      | YARN_RESOURCEMANAGER_HEAPSIZE        |
*--------------------------------------+--------------------------------------+
| NodeManager                          | YARN_NODEMANAGER_HEAPSIZE            |
*--------------------------------------+--------------------------------------+
| WebAppProxy                          | YARN_PROXYSERVER_HEAPSIZE            |
*--------------------------------------+--------------------------------------+
| Map Reduce Job History Server        | HADOOP_JOB_HISTORYSERVER_HEAPSIZE    |
*--------------------------------------+--------------------------------------+

** {Configuring the Hadoop Daemons in Non-Secure Mode}

    This section deals with important parameters to be specified in
    the given configuration files:

    * <<<conf/core-site.xml>>>

*-------------------------+-------------------------+------------------------+
|| Parameter              || Value                  || Notes                 |
*-------------------------+-------------------------+------------------------+
| <<<fs.defaultFS>>>      | NameNode URI            | <hdfs://host:port/>    |
*-------------------------+-------------------------+------------------------+
| <<<io.file.buffer.size>>> | 131072 |  |
| | | Size of read/write buffer used in SequenceFiles. |
*-------------------------+-------------------------+------------------------+

    * <<<conf/hdfs-site.xml>>>

      * Configurations for NameNode:

*-------------------------+-------------------------+------------------------+
|| Parameter              || Value                  || Notes                 |
*-------------------------+-------------------------+------------------------+
| <<<dfs.namenode.name.dir>>> | | |
| | Path on the local filesystem where the NameNode stores the namespace | |
| | and transactions logs persistently. | |
| | | If this is a comma-delimited list of directories then the name table is  |
| | | replicated in all of the directories, for redundancy. |
*-------------------------+-------------------------+------------------------+
| <<<dfs.namenode.hosts>>> / <<<dfs.namenode.hosts.exclude>>> | | |
| | List of permitted/excluded DataNodes. | |
| | | If necessary, use these files to control the list of allowable |
| | | datanodes. |
*-------------------------+-------------------------+------------------------+
| <<<dfs.blocksize>>> | 268435456 | |
| | | HDFS blocksize of 256MB for large file-systems. |
*-------------------------+-------------------------+------------------------+
| <<<dfs.namenode.handler.count>>> | 100 | |
| | | More NameNode server threads to handle RPCs from large number of |
| | | DataNodes. |
*-------------------------+-------------------------+------------------------+

      * Configurations for DataNode:

*-------------------------+-------------------------+------------------------+
|| Parameter              || Value                  || Notes                 |
*-------------------------+-------------------------+------------------------+
| <<<dfs.datanode.data.dir>>> | | |
| | Comma separated list of paths on the local filesystem of a | |
| | <<<DataNode>>> where it should store its blocks. | |
| | | If this is a comma-delimited list of directories, then data will be |
| | | stored in all named directories, typically on different devices. |
*-------------------------+-------------------------+------------------------+

    * <<<conf/yarn-site.xml>>>

      * Configurations for ResourceManager and NodeManager:

*-------------------------+-------------------------+------------------------+
|| Parameter              || Value                  || Notes                 |
*-------------------------+-------------------------+------------------------+
| <<<yarn.acl.enable>>> | | |
| | <<<true>>> / <<<false>>> | |
| | | Enable ACLs? Defaults to <false>. |
*-------------------------+-------------------------+------------------------+
| <<<yarn.admin.acl>>> | | |
| | Admin ACL | |
| | | ACL to set admins on the cluster. |
| | | ACLs are of for <comma-separated-users><space><comma-separated-groups>. |
| | | Defaults to special value of <<*>> which means <anyone>. |
| | | Special value of just <space> means no one has access. |
*-------------------------+-------------------------+------------------------+
| <<<yarn.log-aggregation-enable>>> | | |
| | <false> | |
| | | Configuration to enable or disable log aggregation |
*-------------------------+-------------------------+------------------------+


      * Configurations for ResourceManager:

*-------------------------+-------------------------+------------------------+
|| Parameter              || Value                  || Notes                 |
*-------------------------+-------------------------+------------------------+
| <<<yarn.resourcemanager.address>>> | | |
| | <<<ResourceManager>>> host:port for clients to submit jobs. | |
| | | <host:port>\ |
| | | If set, overrides the hostname set in <<<yarn.resourcemanager.hostname>>>. |
*-------------------------+-------------------------+------------------------+
| <<<yarn.resourcemanager.scheduler.address>>> | | |
| | <<<ResourceManager>>> host:port for ApplicationMasters to talk to | |
| | Scheduler to obtain resources. | |
| | | <host:port>\ |
| | | If set, overrides the hostname set in <<<yarn.resourcemanager.hostname>>>. |
*-------------------------+-------------------------+------------------------+
| <<<yarn.resourcemanager.resource-tracker.address>>> | | |
| | <<<ResourceManager>>> host:port for NodeManagers. | |
| | | <host:port>\ |
| | | If set, overrides the hostname set in <<<yarn.resourcemanager.hostname>>>. |
*-------------------------+-------------------------+------------------------+
| <<<yarn.resourcemanager.admin.address>>> | | |
| | <<<ResourceManager>>> host:port for administrative commands. | |
| | | <host:port>\ |
| | | If set, overrides the hostname set in <<<yarn.resourcemanager.hostname>>>. |
*-------------------------+-------------------------+------------------------+
| <<<yarn.resourcemanager.webapp.address>>> | | |
| | <<<ResourceManager>>> web-ui host:port. | |
| | | <host:port>\ |
| | | If set, overrides the hostname set in <<<yarn.resourcemanager.hostname>>>. |
*-------------------------+-------------------------+------------------------+
| <<<yarn.resourcemanager.hostname>>> | | |
| | <<<ResourceManager>>> host. | |
| | | <host>\ |
| | | Single hostname that can be set in place of setting all <<<yarn.resourcemanager*address>>> resources.  Results in default ports for ResourceManager components. |
*-------------------------+-------------------------+------------------------+
| <<<yarn.resourcemanager.scheduler.class>>> | | |
| | <<<ResourceManager>>> Scheduler class. | |
| | | <<<CapacityScheduler>>> (recommended), <<<FairScheduler>>> (also recommended), or <<<FifoScheduler>>> |
*-------------------------+-------------------------+------------------------+
| <<<yarn.scheduler.minimum-allocation-mb>>> | | |
| | Minimum limit of memory to allocate to each container request at the <<<Resource Manager>>>. | |
| | | In MBs |
*-------------------------+-------------------------+------------------------+
| <<<yarn.scheduler.maximum-allocation-mb>>> | | |
| | Maximum limit of memory to allocate to each container request at the <<<Resource Manager>>>. | |
| | | In MBs |
*-------------------------+-------------------------+------------------------+
| <<<yarn.resourcemanager.nodes.include-path>>> / | | |
| <<<yarn.resourcemanager.nodes.exclude-path>>> | | |
| | List of permitted/excluded NodeManagers. | |
| | | If necessary, use these files to control the list of allowable |
| | | NodeManagers. |
*-------------------------+-------------------------+------------------------+

      * Configurations for NodeManager:

*-------------------------+-------------------------+------------------------+
|| Parameter              || Value                  || Notes                 |
*-------------------------+-------------------------+------------------------+
| <<<yarn.nodemanager.resource.memory-mb>>> | | |
| | Resource i.e. available physical memory, in MB, for given <<<NodeManager>>> | |
| | | Defines total available resources on the <<<NodeManager>>> to be made |
| | | available to running containers |
*-------------------------+-------------------------+------------------------+
| <<<yarn.nodemanager.vmem-pmem-ratio>>> | | |
| | Maximum ratio by which virtual memory usage of tasks may exceed |
| | physical memory | |
| | | The virtual memory usage of each task may exceed its physical memory |
| | | limit by this ratio. The total amount of virtual memory used by tasks |
| | | on the NodeManager may exceed its physical memory usage by this ratio. |
*-------------------------+-------------------------+------------------------+
| <<<yarn.nodemanager.local-dirs>>> | | |
| | Comma-separated list of paths on the local filesystem where | |
| | intermediate data is written. ||
| | | Multiple paths help spread disk i/o. |
*-------------------------+-------------------------+------------------------+
| <<<yarn.nodemanager.log-dirs>>> | | |
| | Comma-separated list of paths on the local filesystem where logs  | |
| | are written. | |
| | | Multiple paths help spread disk i/o. |
*-------------------------+-------------------------+------------------------+
| <<<yarn.nodemanager.log.retain-seconds>>> | | |
| | <10800> | |
| | | Default time (in seconds) to retain log files on the NodeManager |
| | | Only applicable if log-aggregation is disabled. |
*-------------------------+-------------------------+------------------------+
| <<<yarn.nodemanager.remote-app-log-dir>>> | | |
| | </logs> | |
| | | HDFS directory where the application logs are moved on application |
| | | completion. Need to set appropriate permissions. |
| | | Only applicable if log-aggregation is enabled. |
*-------------------------+-------------------------+------------------------+
| <<<yarn.nodemanager.remote-app-log-dir-suffix>>> | | |
| | <logs> | |
| | | Suffix appended to the remote log dir. Logs will be aggregated to  |
| | | $\{yarn.nodemanager.remote-app-log-dir\}/$\{user\}/$\{thisParam\} |
| | | Only applicable if log-aggregation is enabled. |
*-------------------------+-------------------------+------------------------+
| <<<yarn.nodemanager.aux-services>>> | | |
| | mapreduce_shuffle  | |
| | | Shuffle service that needs to be set for Map Reduce applications. |
*-------------------------+-------------------------+------------------------+

      * Configurations for History Server (Needs to be moved elsewhere):

*-------------------------+-------------------------+------------------------+
|| Parameter              || Value                  || Notes                 |
*-------------------------+-------------------------+------------------------+
| <<<yarn.log-aggregation.retain-seconds>>> | | |
| | <-1> | |
| | | How long to keep aggregation logs before deleting them. -1 disables. |
| | | Be careful, set this too small and you will spam the name node. |
*-------------------------+-------------------------+------------------------+
| <<<yarn.log-aggregation.retain-check-interval-seconds>>> | | |
| | <-1> | |
| | | Time between checks for aggregated log retention. If set to 0 or a |
| | | negative value then the value is computed as one-tenth of the |
| | | aggregated log retention time. |
| | | Be careful, set this too small and you will spam the name node. |
*-------------------------+-------------------------+------------------------+



    * <<<conf/mapred-site.xml>>>

      * Configurations for MapReduce Applications:

*-------------------------+-------------------------+------------------------+
|| Parameter              || Value                  || Notes                 |
*-------------------------+-------------------------+------------------------+
| <<<mapreduce.framework.name>>> | | |
| | yarn | |
| | | Execution framework set to Hadoop YARN. |
*-------------------------+-------------------------+------------------------+
| <<<mapreduce.map.memory.mb>>> | 1536 | |
| | | Larger resource limit for maps. |
*-------------------------+-------------------------+------------------------+
| <<<mapreduce.map.java.opts>>> | -Xmx1024M | |
| | | Larger heap-size for child jvms of maps. |
*-------------------------+-------------------------+------------------------+
| <<<mapreduce.reduce.memory.mb>>> | 3072 | |
| | | Larger resource limit for reduces. |
*-------------------------+-------------------------+------------------------+
| <<<mapreduce.reduce.java.opts>>> | -Xmx2560M | |
| | | Larger heap-size for child jvms of reduces. |
*-------------------------+-------------------------+------------------------+
| <<<mapreduce.task.io.sort.mb>>> | 512 | |
| | | Higher memory-limit while sorting data for efficiency. |
*-------------------------+-------------------------+------------------------+
| <<<mapreduce.task.io.sort.factor>>> | 100 | |
| | | More streams merged at once while sorting files. |
*-------------------------+-------------------------+------------------------+
| <<<mapreduce.reduce.shuffle.parallelcopies>>> | 50 | |
| | | Higher number of parallel copies run by reduces to fetch outputs |
| | | from very large number of maps. |
*-------------------------+-------------------------+------------------------+

      * Configurations for MapReduce JobHistory Server:

*-------------------------+-------------------------+------------------------+
|| Parameter              || Value                  || Notes                 |
*-------------------------+-------------------------+------------------------+
| <<<mapreduce.jobhistory.address>>> | | |
| | MapReduce JobHistory Server <host:port> | Default port is 10020. |
*-------------------------+-------------------------+------------------------+
| <<<mapreduce.jobhistory.webapp.address>>> | | |
| | MapReduce JobHistory Server Web UI <host:port> | Default port is 19888. |
*-------------------------+-------------------------+------------------------+
| <<<mapreduce.jobhistory.intermediate-done-dir>>> | /mr-history/tmp | |
|  | | Directory where history files are written by MapReduce jobs. |
*-------------------------+-------------------------+------------------------+
| <<<mapreduce.jobhistory.done-dir>>> | /mr-history/done| |
| | | Directory where history files are managed by the MR JobHistory Server. |
*-------------------------+-------------------------+------------------------+

* {Hadoop Rack Awareness}

    The HDFS and the YARN components are rack-aware.

    The NameNode and the ResourceManager obtains the rack information of the
    slaves in the cluster by invoking an API <resolve> in an administrator
    configured module.

    The API resolves the DNS name (also IP address) to a rack id.

    The site-specific module to use can be configured using the configuration
    item <<<topology.node.switch.mapping.impl>>>. The default implementation
    of the same runs a script/command configured using
    <<<topology.script.file.name>>>. If <<<topology.script.file.name>>> is
    not set, the rack id </default-rack> is returned for any passed IP address.

* {Monitoring Health of NodeManagers}

    Hadoop provides a mechanism by which administrators can configure the
    NodeManager to run an administrator supplied script periodically to
    determine if a node is healthy or not.

    Administrators can determine if the node is in a healthy state by
    performing any checks of their choice in the script. If the script
    detects the node to be in an unhealthy state, it must print a line to
    standard output beginning with the string ERROR. The NodeManager spawns
    the script periodically and checks its output. If the script's output
    contains the string ERROR, as described above, the node's status is
    reported as <<<unhealthy>>> and the node is black-listed by the
    ResourceManager. No further tasks will be assigned to this node.
    However, the NodeManager continues to run the script, so that if the
    node becomes healthy again, it will be removed from the blacklisted nodes
    on the ResourceManager automatically. The node's health along with the
    output of the script, if it is unhealthy, is available to the
    administrator in the ResourceManager web interface. The time since the
    node was healthy is also displayed on the web interface.

    The following parameters can be used to control the node health
    monitoring script in <<<conf/yarn-site.xml>>>.

*-------------------------+-------------------------+------------------------+
|| Parameter              || Value                  || Notes                 |
*-------------------------+-------------------------+------------------------+
| <<<yarn.nodemanager.health-checker.script.path>>> | | |
| | Node health script  | |
| | | Script to check for node's health status. |
*-------------------------+-------------------------+------------------------+
| <<<yarn.nodemanager.health-checker.script.opts>>> | | |
| | Node health script options  | |
| | | Options for script to check for node's health status. |
*-------------------------+-------------------------+------------------------+
| <<<yarn.nodemanager.health-checker.script.interval-ms>>> | | |
| | Node health script interval  | |
| | | Time interval for running health script. |
*-------------------------+-------------------------+------------------------+
| <<<yarn.nodemanager.health-checker.script.timeout-ms>>> | | |
| | Node health script timeout interval  | |
| | | Timeout for health script execution. |
*-------------------------+-------------------------+------------------------+

  The health checker script is not supposed to give ERROR if only some of the
  local disks become bad. NodeManager has the ability to periodically check
  the health of the local disks (specifically checks nodemanager-local-dirs
  and nodemanager-log-dirs) and after reaching the threshold of number of
  bad directories based on the value set for the config property
  yarn.nodemanager.disk-health-checker.min-healthy-disks, the whole node is
  marked unhealthy and this info is sent to resource manager also. The boot
  disk is either raided or a failure in the boot disk is identified by the
  health checker script.

* {Slaves file}

  Typically you choose one machine in the cluster to act as the NameNode and
  one machine as to act as the ResourceManager, exclusively. The rest of the
  machines act as both a DataNode and NodeManager and are referred to as
  <slaves>.

  List all slave hostnames or IP addresses in your <<<conf/slaves>>> file,
  one per line.

* {Logging}

  Hadoop uses the Apache log4j via the Apache Commons Logging framework for
  logging. Edit the <<<conf/log4j.properties>>> file to customize the
  Hadoop daemons' logging configuration (log-formats and so on).

* {Operating the Hadoop Cluster}

  Once all the necessary configuration is complete, distribute the files to the
  <<<HADOOP_CONF_DIR>>> directory on all the machines.

** Hadoop Startup

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

  Format a new distributed filesystem:

----
$ $HADOOP_PREFIX/bin/hdfs namenode -format <cluster_name>
----

  Start the HDFS with the following command, run on the designated NameNode:

----
$ $HADOOP_PREFIX/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR --script hdfs start namenode
----    	

  Run a script to start DataNodes on all slaves:

----
$ $HADOOP_PREFIX/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR --script hdfs start datanode
----    	

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

----
$ $HADOOP_YARN_HOME/sbin/yarn-daemon.sh --config $HADOOP_CONF_DIR start resourcemanager
----    	

  Run a script to start NodeManagers on all slaves:

----
$ $HADOOP_YARN_HOME/sbin/yarn-daemon.sh --config $HADOOP_CONF_DIR start nodemanager
----    	

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

----
$ $HADOOP_YARN_HOME/sbin/yarn-daemon.sh start proxyserver --config $HADOOP_CONF_DIR
----

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

----
$ $HADOOP_PREFIX/sbin/mr-jobhistory-daemon.sh start historyserver --config $HADOOP_CONF_DIR
----    	

** Hadoop Shutdown

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

----
$ $HADOOP_PREFIX/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR --script hdfs stop namenode
----    	

  Run a script to stop DataNodes on all slaves:

----
$ $HADOOP_PREFIX/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR --script hdfs stop datanode
----    	

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

----
$ $HADOOP_YARN_HOME/sbin/yarn-daemon.sh --config $HADOOP_CONF_DIR stop resourcemanager
----    	

  Run a script to stop NodeManagers on all slaves:

----
$ $HADOOP_YARN_HOME/sbin/yarn-daemon.sh --config $HADOOP_CONF_DIR stop nodemanager
----    	

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

----
$ $HADOOP_YARN_HOME/sbin/yarn-daemon.sh stop proxyserver --config $HADOOP_CONF_DIR
----


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

----
$ $HADOOP_PREFIX/sbin/mr-jobhistory-daemon.sh stop historyserver --config $HADOOP_CONF_DIR
----    	


* {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 section also describes the various Unix users who should be starting the
  various components and uses the same Unix accounts and groups used previously:

** Hadoop Startup

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

    Format a new distributed filesystem as <hdfs>:

----
[hdfs]$ $HADOOP_PREFIX/bin/hdfs namenode -format <cluster_name>
----

    Start the HDFS with the following command, run on the designated NameNode
    as <hdfs>:

----
[hdfs]$ $HADOOP_PREFIX/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR --script hdfs start namenode
----    	

    Run a script to start DataNodes on all slaves as <root> with a special
    environment variable <<<HADOOP_SECURE_DN_USER>>> set to <hdfs>:

----
[root]$ HADOOP_SECURE_DN_USER=hdfs $HADOOP_PREFIX/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR --script hdfs start datanode
----    	

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

----
[yarn]$ $HADOOP_YARN_HOME/sbin/yarn-daemon.sh --config $HADOOP_CONF_DIR start resourcemanager
----    	

    Run a script to start NodeManagers on all slaves as <yarn>:

----
[yarn]$ $HADOOP_YARN_HOME/sbin/yarn-daemon.sh --config $HADOOP_CONF_DIR 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_YARN_HOME/bin/yarn start proxyserver --config $HADOOP_CONF_DIR
----    	

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

----
[mapred]$ $HADOOP_PREFIX/sbin/mr-jobhistory-daemon.sh start historyserver --config $HADOOP_CONF_DIR
----    	

** Hadoop Shutdown

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

----
[hdfs]$ $HADOOP_PREFIX/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR --script hdfs stop namenode
----    	

  Run a script to stop DataNodes on all slaves as <root>:

----
[root]$ $HADOOP_PREFIX/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR --script hdfs stop datanode
----    	

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

----
[yarn]$ $HADOOP_YARN_HOME/sbin/yarn-daemon.sh --config $HADOOP_CONF_DIR stop resourcemanager
----    	

  Run a script to stop NodeManagers on all slaves as <yarn>:

----
[yarn]$ $HADOOP_YARN_HOME/sbin/yarn-daemon.sh --config $HADOOP_CONF_DIR stop nodemanager
----    	

  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_YARN_HOME/bin/yarn stop proxyserver --config $HADOOP_CONF_DIR
----

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

----
[mapred]$ $HADOOP_PREFIX/sbin/mr-jobhistory-daemon.sh stop historyserver --config $HADOOP_CONF_DIR
----    	

* {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 50070. |
*-------------------------+-------------------------+------------------------+
| ResourceManager | http://<rm_host:port>/ | Default HTTP port is 8088. |
*-------------------------+-------------------------+------------------------+
| MapReduce JobHistory Server | http://<jhs_host:port>/ | |
| | | Default HTTP port is 19888. |
*-------------------------+-------------------------+------------------------+