Hadoop入门（一）：Hadoop伪分布安装

1安装Hadoop

首先解压下载来的hadoop 0.20包到/home/admin目录：

tar xzfhadoop-0.20.2.tar.gz

配置Hadoop环境变量：

exportHADOOP_INSTALL=/home/admin/hadoop-0.20.2

exportPATH=$PATH:$HADOOP_INSTALL/bin

测试下是否安装成功：

hadoop version

2创建SSH无密码模式密钥

为当前用户配置无密码的SSH登录：

         ssh-keygen-t rsa -P '' -f ~/.ssh/id_rsa

cat~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys

测试一下是否还提示输入密码：

ssh localhost

3配置Hadoop伪分布模式

/home/admin/hadoop-0.20.2/conf/core-site.xml

===============================================================================

<configuration>

       <property>

               <name>fs.default.name</name>

               <value>hdfs://localhost</value>

       </property>

</configuration>

/home/admin/hadoop-0.20.2/conf/hdfs-site.xml

===============================================================================

<configuration>

       <property>

               <name>dfs.replication</name>

                <value>1</value>

       </property>

</configuration>

/home/admin/hadoop-0.20.2/conf/mapred-site.xml

===============================================================================

<configuration>

       <property>

               <name>mapred.job.tracker</name>

               <value>localhost:8021</value>

       </property>

</configuration>

4启动Hadoop服务

4.1格式化NameNode

hadoop namenode -format

4.2启动服务

start-dfs.sh

start-mapred.sh

4.3常见问题

在namenode启动脚本%HADOOP_HOME%/bin/start-dfs.sh的时候发现datanode报错：

Error: JAVA_HOMEis not set

原因是在%HADOOP_HOME%/conf/hadoop-env.sh内缺少JAVA_HOME的定义，只需要在hadoop-env.sh中增加：

exportJAVA_HOME=/export/servers/jdk1.6.0_25/

5测试HDFS

hadoop fs -mkdir books

hadoop fs -ls .

hadoop fs -copyFromLocal NOTICE.txthdfs://localhost/user/root/books/NOTICE.txt

参考资料

《Hadoop权威指南》