安装hadoop

1、环境变量

export JAVA_HOME=/root/soft/jdk8

export CLASSPATH=.:$JAVA_HOME/lib:$JAVA_HOME/lib/tools.jar:$JAVA_HOME/lib/dt.jar

export HADOOP_HOME=/root/soft/hdp312

export PATH=$PATH:$MAVEN_HOME/bin:$JAVA_HOME/bin:$HADOOP_HOME/bin:$HADOOP_HOME/sbin

2、三种方式启动集群

• Local (Standalone) Mode
• Pseudo-Distributed Mode
• Fully-Distributed Mode

3、实操

hadoop 命令启动驱动时，程序会利用Configuration API来加载默认配置目录下下的配置文件

所以可以指定-conf  来覆盖默认配置比如连接信息

Standalone Operation

拷贝安装目录中配置/etc/hadoop到一个新的目录devconf/hadoop/，修改其中的配置文件为本地运行模式

   core-site.xml:

<configuration>
    <property>
        <name>fs.defaultFS</name>
        <value>file:///</value>
    </property>
</configuration>

mapred-site.xml:

<configuration>
    <property>
        <name>mapreduce.framework.name</name>
        <value>local</value>
    </property>
</configuration>

By default, Hadoop is configured to run in a non-distributed mode, as a single Java process. This is useful for debugging.

The following example copies the unpacked conf directory to use as input and then finds and displays every match of the given regular expression. Output is written to the given output directory.

  $ mkdir input
  $ cp etc/hadoop/*.xml input

    export HADOOP_CONF_DIR=/root/soft/hdp312/devconf/hadoop/

 $ bin/hadoop jar share/hadoop/mapreduce/hadoop-mapreduce-examples-3.2.0.jar grep input output 'dfs[a-z.]+' $ cat output/*

注意：export HADOOP_CONF_DIR=/root/soft/hdp312/devconf/hadoop/

Pseudo-Distributed Operation

改变HADOOP_CONF_DIR指向伪分布式配置

etc/hadoop/core-site.xml:

<configuration>
    <property>
        <name>fs.defaultFS</name>
        <value>hdfs://localhost:9000</value>
    </property>
</configuration>

etc/hadoop/hdfs-site.xml:

<configuration>
    <property>
        <name>dfs.replication</name>
        <value>1</value>
    </property>
</configuration>

mapred-site.xml:

<configuration>
    <property>
        <name>mapreduce.framework.name</name>
        <value>yarn</value>
    </property>   

    <property>
        <name>mapreduce.application.classpath</name>
        <value>$HADOOP_MAPRED_HOME/share/hadoop/mapreduce/*:$HADOOP_MAPRED_HOME/share/hadoop/mapreduce/lib/*</value>
    </property>
</configuration>

yarn-site.xml:

<configuration>
    <property>
        <name>yarn.nodemanager.aux-services</name>
        <value>mapreduce_shuffle</value>
    </property>
    <property>
        <name>yarn.nodemanager.env-whitelist</name>
        <value>JAVA_HOME,HADOOP_COMMON_HOME,HADOOP_HDFS_HOME,HADOOP_CONF_DIR,CLASSPATH_PREPEND_DISTCACHE,HADOOP_YARN_HOME,HADOOP_MAPRED_HOME</value>
    </property>
</configuration>

注意：workers中添加数据节点

hdfs dfs -mkdir /input

hdfs dfs -put etc/hadoop/*.xml input

hadoop jar share/hadoop/mapreduce/hadoop-mapreduce-examples-3.1.2.jar grep /input output 'dfs[a-z.]+'#执行作业按照伪分布式方式，在hdfs上运行