hadoop 0.21.0 伪分布式环境搭建（mac雪豹系统）

1.下载hadoop包，[url]http://labs.renren.com/apache-mirror//hadoop/core/hadoop-0.21.0/hadoop-0.21.0.tar.gz[/url]
2.解压 tar xzf hadoop-0.21.0.tar.gz
3.进入hadoop解压后得文件夹，编辑hadoop-env.sh 指定JAVA_HOME变量，比如

export JAVA_HOME=/System/Library/Frameworks/JavaVM.framework/Versions/CurrentJDK/Home

4.edit ~/.bash_profile

export HADOOP_INSTALL=your hadoop directory
export HADOOP_HOME=your hadoop directory
export PATH=$PATH:$HADOOP_INSTALL/bin

5.重新开shell窗口，执行 hadoop version，可以看到如下信息
[quote]
Hadoop 0.21.0
Subversion https://svn.apache.org/repos/asf/hadoop/common/branches/branch-0.21 -r 985326
Compiled by tomwhite on Tue Aug 17 01:02:28 EDT 2010
From source with checksum a1aeb15b4854808d152989ba76f90fac
[/quote]

6 配置ssh，确保你的系统允许远程登录。执行以下命令，
[quote]
ssh-keygen -t rsa -P '' -f ~/.ssh/id_rsa
cat ~/.ssh/id_rsa.pub > ~/.ssh/authorized_keys
[/quote]

7 执行 ssh localhost，如果能不输入密码就可以登录就对了。
8 首次使用hadoop，需要格式化hdfs文件系统。请在hadoop的目录下新建一个logs目录，这个目录是默认用来放置log的地方。执行以下命令
[quote]
hadoop namenode -format
[/quote]
如果没有异常抛出，只有正常的log就对了

9开启守护进程进入hadoop目录的conf子目录，
(1)修改 core-site.xml
[quote]

<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>

<!-- Put site-specific property overrides in this file. -->

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

[/quote]

（2）修改hdfs-site.xml
[quote]
?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>

<!-- Put site-specific property overrides in this file. -->

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

[/quote]
(3) edit mapred-site.xml
[quote]
<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>

<!-- Put site-specific property overrides in this file. -->

<configuration>
<property>
<name>mapred.job.tracker</name>
<value>localhost:8021</value>
</property>

</configuration>

[/quote]

(4)执行
[quote]
start-dfs.sh
start-mapred.sh
[/quote]

现在可以试用hadoop的威力了，如果不会用hadoop，这里有使用python的脚本方法
[url]
http://packages.python.org/mrjob/writing-and-running.html#running-on-your-own-hadoop-cluster
[/url]
只需要执行
[quote]python your_mr_job_sub_class.py -r hadoop < input > output[/quote]
非常方便

10 停止守护进程
[quote]
stop-dfs.sh
stop-mapred.sh
[/quote]

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