Hadoop---安装Hadoop

   Hadoop是一个开源的框架，可编写和运行分布式应用处理大规模数据。

   运行Hadoop需要Java1.6或更高版本。JDK的下载地址为：http://www.oracle.com/technetwork/java/javase/downloads/jdk-7u3-download-1501626.html

   下载JDK1.6，利用SAMBA，FTP拷到Linux服务器上。

   ./jdk-6u29-linux-i586-rpm.bin得到jdk-6u29-linux-i586.rpm

   rpm -ivh jdk-6u29-linux-i586.rpm

   JDK默认安装在/usr/java下

   接下来就是配置JAVA_HOME目录，vi ~/.bash_profile，添加JAVA_HOME

# User specific environment and startup programs

PATH=$PATH:$HOME/bin
JAVA_HOME=/usr/java/jdk1.6.0_29

export PATH
export JAVA_HOME
unset USERNAME
~

   source ~/.bash_profile使更改的变量值生效。

   Hadoop的下载地址为http://labs.renren.com/apache-mirror/hadoop/common/hadoop-1.0.2/

   将hadoop-1.0.2.tar.gz拷贝到Linux服务器上

   使用tar zxvf hadoop-1.0.2.tar.gz进行解压

   进行解压的文件的bin目录下，例如：/opt/hadoop-1.0.2/bin

   不加任何参数运行Hadoop

   ./hadoop

   得到  

[root@localhost bin]# ./hadoop
Usage: hadoop [--config confdir] COMMAND
where COMMAND is one of:
  namenode -format     format the DFS filesystem
  secondarynamenode    run the DFS secondary namenode
  namenode             run the DFS namenode
  datanode             run a DFS datanode
  dfsadmin             run a DFS admin client
  mradmin              run a Map-Reduce admin client
  fsck                 run a DFS filesystem checking utility
  fs                   run a generic filesystem user client
  balancer             run a cluster balancing utility
  fetchdt              fetch a delegation token from the NameNode
  jobtracker           run the MapReduce job Tracker node
  pipes                run a Pipes job
  tasktracker          run a MapReduce task Tracker node
  historyserver        run job history servers as a standalone daemon
  job                  manipulate MapReduce jobs
  queue                get information regarding JobQueues
  version              print the version
  jar             run a jar file
  distcp   copy file or directories recursively
  archive -archiveName NAME -p  *  create a hadoop archive
  classpath            prints the class path needed to get the
                       Hadoop jar and the required libraries
  daemonlog            get/set the log level for each daemon
 or
  CLASSNAME            run the class named CLASSNAME
Most commands print help when invoked w/o parameters.

   各参数的中文描述为：

[root@localhost bin]# ./hadoop
Usage: hadoop [--config confdir] COMMAND
where COMMAND is one of:
  namenode -format     格式化DFS文件系统
  secondarynamenode    运行DFS的第二个namenode
  namenode             运行DFS的namenode
  datanode             运行一个DFS的datanode
  dfsadmin             运行一个DFS的admin客户端
  mradmin              运行一个MapReduce的admin客户端
  fsck                 运行一个DFS文件系统的检查工具
  fs                   运行一个普通的文件系统用户客户端
  balancer             运行一个集群负载均衡工具
  fetchdt              从NameNode取一行词
  jobtracker           运行MapReduce的Tracker 节点
  pipes                运行 Pipes 作业
  tasktracker          运行MapReduce的task Tracker 节点
  historyserver        运行一个独立的history server守护进程
  job                  处理MapReduce作业
  queue                得到JobQueues的信息
  version              打印版本
  jar <jar>            运行一个 jar file
  distcp <srcurl> <desturl> 递归地复制文件或者目录
  archive -archiveName NAME -p <parent path> <src>* <dest> 生成一个Hadoop档案
  classpath            打印找到Hadoop jar and the required libraries 所需要的目录
  daemonlog            获取每个daemon的日志级别
 or
  CLASSNAME            运行名为CLASSNAME的类大多数命令会在使用w/o参数时打印出帮助信息
Most commands print help when invoked w/o parameters.

如运行./hadoop classpath，我们得到

[root@localhost bin]# ./hadoop classpath
/opt/hadoop-1.0.2/libexec/../conf:/usr/java/jdk1.6.0_29/lib/tools.jar:/opt/hadoop-1.0.2/libexec/..:/opt/hadoop-1.0.2/libexec/../hadoop-core-1.0.2.jar:/opt/hadoop-1.0.2/libexec/../lib/asm-3.2.jar:/opt/hadoop-1.0.2/libexec/../lib/aspectjrt-1.6.5.jar:/opt/hadoop-1.0.2/libexec/../lib/aspectjtools-1.6.5.jar:/opt/hadoop-1.0.2/libexec/../lib/commons-beanutils-1.7.0.jar:/opt/hadoop-1.0.2/libexec/../lib/commons-beanutils-core-1.8.0.jar:/opt/hadoop-1.0.2/libexec/../lib/commons-cli-1.2.jar:/opt/hadoop-1.0.2/libexec/../lib/commons-codec-1.4.jar:/opt/hadoop-1.0.2/libexec/../lib/commons-collections-3.2.1.jar:/opt/hadoop-1.0.2/libexec/../lib/commons-configuration-1.6.jar:/opt/hadoop-1.0.2/libexec/../lib/commons-daemon-1.0.1.jar:/opt/hadoop-1.0.2/libexec/../lib/commons-digester-1.8.jar:/opt/hadoop-1.0.2/libexec/../lib/commons-el-1.0.jar:/opt/hadoop-1.0.2/libexec/../lib/commons-httpclient-3.0.1.jar:/opt/hadoop-1.0.2/libexec/../lib/commons-lang-2.4.jar:/opt/hadoop-1.0.2/libexec/../lib/commons-logging-1.1.1.jar:/opt/hadoop-1.0.2/libexec/../lib/commons-logging-api-1.0.4.jar:/opt/hadoop-1.0.2/libexec/../lib/commons-math-2.1.jar:/opt/hadoop-1.0.2/libexec/../lib/commons-net-1.4.1.jar:/opt/hadoop-1.0.2/libexec/../lib/core-3.1.1.jar:/opt/hadoop-1.0.2/libexec/../lib/hadoop-capacity-scheduler-1.0.2.jar:/opt/hadoop-1.0.2/libexec/../lib/hadoop-fairscheduler-1.0.2.jar:/opt/hadoop-1.0.2/libexec/../lib/hadoop-thriftfs-1.0.2.jar:/opt/hadoop-1.0.2/libexec/../lib/hsqldb-1.8.0.10.jar:/opt/hadoop-1.0.2/libexec/../lib/jackson-core-asl-1.8.8.jar:/opt/hadoop-1.0.2/libexec/../lib/jackson-mapper-asl-1.8.8.jar:/opt/hadoop-1.0.2/libexec/../lib/jasper-compiler-5.5.12.jar:/opt/hadoop-1.0.2/libexec/../lib/jasper-runtime-5.5.12.jar:/opt/hadoop-1.0.2/libexec/../lib/jdeb-0.8.jar:/opt/hadoop-1.0.2/libexec/../lib/jersey-core-1.8.jar:/opt/hadoop-1.0.2/libexec/../lib/jersey-json-1.8.jar:/opt/hadoop-1.0.2/libexec/../lib/jersey-server-1.8.jar:/opt/hadoop-1.0.2/libexec/../lib/jets3t-0.6.1.jar:/opt/hadoop-1.0.2/libexec/../lib/jetty-6.1.26.jar:/opt/hadoop-1.0.2/libexec/../lib/jetty-util-6.1.26.jar:/opt/hadoop-1.0.2/libexec/../lib/jsch-0.1.42.jar:/opt/hadoop-1.0.2/libexec/../lib/junit-4.5.jar:/opt/hadoop-1.0.2/libexec/../lib/kfs-0.2.2.jar:/opt/hadoop-1.0.2/libexec/../lib/log4j-1.2.15.jar:/opt/hadoop-1.0.2/libexec/../lib/mockito-all-1.8.5.jar:/opt/hadoop-1.0.2/libexec/../lib/oro-2.0.8.jar:/opt/hadoop-1.0.2/libexec/../lib/servlet-api-2.5-20081211.jar:/opt/hadoop-1.0.2/libexec/../lib/slf4j-api-1.4.3.jar:/opt/hadoop-1.0.2/libexec/../lib/slf4j-log4j12-1.4.3.jar:/opt/hadoop-1.0.2/libexec/../lib/xmlenc-0.52.jar:/opt/hadoop-1.0.2/libexec/../lib/jsp-2.1/jsp-2.1.jar:/opt/hadoop-1.0.2/libexec/../lib/jsp-2.1/jsp-api-2.1.jar

由上可知，运行一个（Java）Hadoop程序的命令为hadoop jar。就像命令显示的那样，用Java写的Hadoop程序被打包为jar执行文件。

在Hadoop的目录下，有一个名为hadoop-examples-1.0.2.jar的文件（不同版本的Hadoop,jar文件不同），jar里打包了一些例子。可以在hadoop-1.0.2/src/examples/org/apache/hadoop/examples目录下找到这些例子。例子如下：

[root@localhost examples]# ll
total 228
-rw-rw-r-- 1 root root  2797 Mar 25 08:01 AggregateWordCount.java
-rw-rw-r-- 1 root root  2879 Mar 25 08:01 AggregateWordHistogram.java
drwxr-xr-x 2 root root  4096 Apr 11 21:50 dancing
-rw-rw-r-- 1 root root 13089 Mar 25 08:01 DBCountPageView.java
-rw-rw-r-- 1 root root  3751 Mar 25 08:01 ExampleDriver.java
-rw-rw-r-- 1 root root  3334 Mar 25 08:01 Grep.java
-rw-rw-r-- 1 root root  6582 Mar 25 08:01 Join.java
-rw-rw-r-- 1 root root  8282 Mar 25 08:01 MultiFileWordCount.java
-rw-rw-r-- 1 root root   853 Mar 25 08:01 package.html
-rw-rw-r-- 1 root root 11914 Mar 25 08:01 PiEstimator.java
-rw-rw-r-- 1 root root 40350 Mar 25 08:01 RandomTextWriter.java
-rw-rw-r-- 1 root root 10190 Mar 25 08:01 RandomWriter.java
-rw-rw-r-- 1 root root  7809 Mar 25 08:01 SecondarySort.java
-rw-rw-r-- 1 root root  9156 Mar 25 08:01 SleepJob.java
-rw-rw-r-- 1 root root  8040 Mar 25 08:01 Sort.java
drwxr-xr-x 2 root root  4096 Apr 11 21:50 terasort
-rw-rw-r-- 1 root root  2395 Mar 25 08:01 WordCount.java

 我们使用WordCount来试运行一个Hadoop。

 不指定任何参数执行wordcount将显示一些有关用法的信息：

[root@localhost bin]# ./hadoop jar /opt/hadoop-1.0.2/hadoop-examples-1.0.2.jar wordcount
Usage: wordcount <in> <out>

 从网上下载一篇英文散文，保存为test.txt,保存在/opt/data目录下

 再次执行wordcount得到

[root@localhost bin]# ./hadoop jar /opt/hadoop-1.0.2/hadoop-examples-1.0.2.jar wordcount /opt/data/test.txt /opt/data/output
12/04/11 22:48:41 INFO util.NativeCodeLoader: Loaded the native-hadoop library
****file:/opt/data/test.txt
12/04/11 22:48:41 INFO input.FileInputFormat: Total input paths to process : 1
12/04/11 22:48:41 WARN snappy.LoadSnappy: Snappy native library not loaded
12/04/11 22:48:42 INFO mapred.JobClient: Running job: job_local_0001
12/04/11 22:48:42 INFO util.ProcessTree: setsid exited with exit code 0
12/04/11 22:48:42 INFO mapred.Task:  Using ResourceCalculatorPlugin : org.apache.hadoop.util.LinuxResourceCalculatorPlugin@9ced8e
12/04/11 22:48:42 INFO mapred.MapTask: io.sort.mb = 100
12/04/11 22:48:43 INFO mapred.MapTask: data buffer = 79691776/99614720
12/04/11 22:48:43 INFO mapred.MapTask: record buffer = 262144/327680
12/04/11 22:48:43 INFO mapred.MapTask: Starting flush of map output
12/04/11 22:48:43 INFO mapred.MapTask: Finished spill 0
12/04/11 22:48:43 INFO mapred.Task: Task:attempt_local_0001_m_000000_0 is done. And is in the process of commiting
12/04/11 22:48:43 INFO mapred.JobClient:  map 0% reduce 0%
12/04/11 22:48:45 INFO mapred.LocalJobRunner:
12/04/11 22:48:45 INFO mapred.Task: Task 'attempt_local_0001_m_000000_0' done.
12/04/11 22:48:45 INFO mapred.Task:  Using ResourceCalculatorPlugin : org.apache.hadoop.util.LinuxResourceCalculatorPlugin@281d4b
12/04/11 22:48:45 INFO mapred.LocalJobRunner:
12/04/11 22:48:45 INFO mapred.Merger: Merging 1 sorted segments
12/04/11 22:48:45 INFO mapred.Merger: Down to the last merge-pass, with 1 segments left of total size: 6079 bytes
12/04/11 22:48:45 INFO mapred.LocalJobRunner:
12/04/11 22:48:45 INFO mapred.Task: Task:attempt_local_0001_r_000000_0 is done. And is in the process of commiting
12/04/11 22:48:45 INFO mapred.LocalJobRunner:
12/04/11 22:48:45 INFO mapred.Task: Task attempt_local_0001_r_000000_0 is allowed to commit now
12/04/11 22:48:45 INFO output.FileOutputCommitter: Saved output of task 'attempt_local_0001_r_000000_0' to /opt/data/output
12/04/11 22:48:46 INFO mapred.JobClient:  map 100% reduce 0%
12/04/11 22:48:48 INFO mapred.LocalJobRunner: reduce > reduce
12/04/11 22:48:48 INFO mapred.Task: Task 'attempt_local_0001_r_000000_0' done.
12/04/11 22:48:49 INFO mapred.JobClient:  map 100% reduce 100%
12/04/11 22:48:49 INFO mapred.JobClient: Job complete: job_local_0001
12/04/11 22:48:49 INFO mapred.JobClient: Counters: 20
12/04/11 22:48:49 INFO mapred.JobClient:   File Output Format Counters
12/04/11 22:48:49 INFO mapred.JobClient:     Bytes Written=4241
12/04/11 22:48:49 INFO mapred.JobClient:   FileSystemCounters
12/04/11 22:48:49 INFO mapred.JobClient:     FILE_BYTES_READ=301803
12/04/11 22:48:49 INFO mapred.JobClient:     FILE_BYTES_WRITTEN=368355
12/04/11 22:48:49 INFO mapred.JobClient:   File Input Format Counters
12/04/11 22:48:49 INFO mapred.JobClient:     Bytes Read=5251
12/04/11 22:48:49 INFO mapred.JobClient:   Map-Reduce Framework
12/04/11 22:48:49 INFO mapred.JobClient:     Map output materialized bytes=6083
12/04/11 22:48:49 INFO mapred.JobClient:     Map input records=21
12/04/11 22:48:49 INFO mapred.JobClient:     Reduce shuffle bytes=0
12/04/11 22:48:49 INFO mapred.JobClient:     Spilled Records=946
12/04/11 22:48:49 INFO mapred.JobClient:     Map output bytes=9182
12/04/11 22:48:49 INFO mapred.JobClient:     Total committed heap usage (bytes)=321134592
12/04/11 22:48:49 INFO mapred.JobClient:     CPU time spent (ms)=0
12/04/11 22:48:49 INFO mapred.JobClient:     SPLIT_RAW_BYTES=88
12/04/11 22:48:49 INFO mapred.JobClient:     Combine input records=970
12/04/11 22:48:49 INFO mapred.JobClient:     Reduce input records=473
12/04/11 22:48:49 INFO mapred.JobClient:     Reduce input groups=473
12/04/11 22:48:49 INFO mapred.JobClient:     Combine output records=473
12/04/11 22:48:49 INFO mapred.JobClient:     Physical memory (bytes) snapshot=0
12/04/11 22:48:49 INFO mapred.JobClient:     Reduce output records=473
12/04/11 22:48:49 INFO mapred.JobClient:     Virtual memory (bytes) snapshot=0
12/04/11 22:48:49 INFO mapred.JobClient:     Map output records=970

查看统计的结果

[root@localhost bin]# more /opt/data/output/*
::::::::::::::
/opt/data/output/part-r-00000
::::::::::::::
"Eat,   1
"How    1
"she    1
And     1
But     1
Darkness        1
Epicurean       1
Eyes".  1
He      1
I       24
If      2
In      1
It      3
Nature  2
Occasionally,   1
Only    1
Particularly    1
Persian 1
Recently        1
So      1
Sometimes       1
Such    1
The     2
Their   1
There   1
To      2
Use     1
We      3
What    1
When    1
Yet,    1

wordcount程序有一些不足，分词完全根据空格而不是根据标点符号，这使得“"Eat”，“eat”,“Eat”分别成为单独的单词。可以修改wordcount.java来修改这个不足

将StringTokenizer itr = new StringTokenizer(line)改为

StringTokenizer itr = new StringTokenizer(line," \t\n\r\f,.:;?![]'")

重新编译再运行一次，得到的结果就好多了。