伪分布式

hadoop的三种安装方式：

安装之前需要

$ sudo apt-get install ssh

$ sudo apt-get install rsync

详见：

伪分布式配置

Configuration

修改下边:

etc/hadoop/core-site.xml:


        
             
      
       fs.defaultFS
              
      
       hdfs://localhost:9000

etc/hadoop/hdfs-site.xml:


        
             
      
       dfs.replication
              
      
       1

配置ssh

$ ssh-keygen -t dsa -P '' -f ~/.ssh/id_dsa  $ cat ~/.ssh/id_dsa.pub >> ~/.ssh/authorized_keys

如果想运行在yarn上

需要执行下边的步骤：

Configure parameters as follows:

etc/hadoop/mapred-site.xml:


          
               
        
         mapreduce.framework.name
                
        
         yarn

etc/hadoop/yarn-site.xml:


          
               
        
         yarn.nodemanager.aux-services
                
        
         mapreduce_shuffle

Start ResourceManager daemon and NodeManager daemon:
```
$ sbin/start-yarn.sh
```

Browse the web interface for the ResourceManager; by default it is available at:
- ResourceManager - http://localhost:8088/

Run a MapReduce job.

When you're done, stop the daemons with:
```
$ sbin/stop-yarn.sh
```

输入：

可以看到

启动yarn后

Format the filesystem:
```
$ bin/hdfs namenode -format
```

Start NameNode daemon and DataNode daemon:
```
$ sbin/start-dfs.sh
```
The hadoop daemon log output is written to the $HADOOP_LOG_DIR directory (defaults to $HADOOP_HOME/logs).

Browse the web interface for the NameNode; by default it is available at:
- NameNode -

输入后得到：

然后执行测试

Make the HDFS directories required to execute MapReduce jobs:

$ bin/hdfs dfs -mkdir /user  $ bin/hdfs dfs -mkdir /user/

Copy the input files into the distributed filesystem:
```
$ bin/hdfs dfs -put etc/hadoop input
```

Run some of the examples provided:

$ bin/hadoop jar share/hadoop/mapreduce/hadoop-mapreduce-examples-2.6.0.jar grep input output 'dfs[a-z.]+'

Examine the output files:
Copy the output files from the distributed filesystem to the local filesystem and examine them:
```
$ bin/hdfs dfs -get output output  $ cat output/*
```
or

View the output files on the distributed filesystem:
```
$ bin/hdfs dfs -cat output/*
```

看运行的情况：

查看结果

测试执行成功，可以编写本地代码了。

eclipse hadoop2.6插件使用

下载源码：

git clone

下载过程：

编译插件：

cd src/contrib/eclipse-plugin

ant jar -Dversion=2.6.0 -Declipse.home=/usr/local/eclipse -Dhadoop.home=/usr/local/hadoop-2.6.0 //路径根据自己的配置

复制编译好的jar到eclipse插件目录，重启eclipse

window ->preference -> hadoop Map/Reduce -> Hadoop installation directory

配置Map/Reduce 视图

window ->Open Perspective -> other->Map/Reduce -> 点击“OK”

windows → show view → other->Map/Reduce Locations-> 点击“OK”

控制台会多出一个“Map/Reduce Locations”的Tab页

在“Map/Reduce Locations” Tab页点击图标<大象+>或者在空白的地方右键，选择“New Hadoop location…”，弹出对话框“New hadoop location…”，配置如下内容：将ha1改为自己的hadoop用户

注意：MR Master和DFS Master配置必须和mapred-site.xml和core-site.xml等配置文件一致。

打开Project Explorer,查看HDFS文件系统。

新建Map/Reduce任务

File->New->project->Map/Reduce Project->Next

编写WordCount类：记得先把服务都起来

/** *  */package com.zongtui;/** * ClassName: WordCount 
 * Function: TODO ADD FUNCTION. 
 * date: Jun 28, 2015 5:34:18 AM 
 * * @author zhangfeng * @version  * @since JDK 1.7 */import java.io.IOException;import java.util.Iterator;import java.util.StringTokenizer;import org.apache.hadoop.fs.Path;import org.apache.hadoop.io.IntWritable;import org.apache.hadoop.io.LongWritable;import org.apache.hadoop.io.Text;import org.apache.hadoop.mapred.FileInputFormat;import org.apache.hadoop.mapred.FileOutputFormat;import org.apache.hadoop.mapred.JobClient;import org.apache.hadoop.mapred.JobConf;import org.apache.hadoop.mapred.MapReduceBase;import org.apache.hadoop.mapred.Mapper;import org.apache.hadoop.mapred.OutputCollector;import org.apache.hadoop.mapred.Reducer;import org.apache.hadoop.mapred.Reporter;import org.apache.hadoop.mapred.TextInputFormat;import org.apache.hadoop.mapred.TextOutputFormat;public class WordCount {    public static class Map extends MapReduceBase implements            Mapper
        
          {        private final static IntWritable one = new IntWritable(1);        private Text word = new Text();        public void map(LongWritable key, Text value,                OutputCollector
         
           output, Reporter reporter)                throws IOException {            String line = value.toString();            StringTokenizer tokenizer = new StringTokenizer(line);            while (tokenizer.hasMoreTokens()) {                word.set(tokenizer.nextToken());                output.collect(word, one);            }        }    }    public static class Reduce extends MapReduceBase implements            Reducer
          
            {        public void reduce(Text key, Iterator
           
             values,                OutputCollector
            
              output, Reporter reporter)                throws IOException {            int sum = 0;            while (values.hasNext()) {                sum += values.next().get();            }            output.collect(key, new IntWritable(sum));        }    }    public static void main(String[] args) throws Exception {        JobConf conf = new JobConf(WordCount.class);        conf.setJobName("wordcount");        conf.setOutputKeyClass(Text.class);        conf.setOutputValueClass(IntWritable.class);        conf.setMapperClass(Map.class);        conf.setReducerClass(Reduce.class);        conf.setInputFormat(TextInputFormat.class);        conf.setOutputFormat(TextOutputFormat.class);        FileInputFormat.setInputPaths(conf, new Path(args[0]));        FileOutputFormat.setOutputPath(conf, new Path(args[1]));        JobClient.runJob(conf);    }}

user/admin123/input/hadoop是你上传在hdfs的文件夹（自己创建），里面放要处理的文件。ouput1放输出结果

将程序放在hadoop集群上运行：右键-->Runas -->Run on Hadoop,最终的输出结果会在HDFS相应的文件夹下显示。至此，ubuntu下hadoop-2.6.0 eclipse插件配置完成。

遇到异常

Exception in thread "main" org.apache.hadoop.mapred.FileAlreadyExistsException: Output directory hdfs://localhost:9000/output already exists    at org.apache.hadoop.mapred.FileOutputFormat.checkOutputSpecs(FileOutputFormat.java:132)    at org.apache.hadoop.mapreduce.JobSubmitter.checkSpecs(JobSubmitter.java:564)    at org.apache.hadoop.mapreduce.JobSubmitter.submitJobInternal(JobSubmitter.java:432)    at org.apache.hadoop.mapreduce.Job$10.run(Job.java:1296)    at org.apache.hadoop.mapreduce.Job$10.run(Job.java:1293)    at java.security.AccessController.doPrivileged(Native Method)    at javax.security.auth.Subject.doAs(Subject.java:415)    at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1628)    at org.apache.hadoop.mapreduce.Job.submit(Job.java:1293)    at org.apache.hadoop.mapred.JobClient$1.run(JobClient.java:562)    at org.apache.hadoop.mapred.JobClient$1.run(JobClient.java:557)    at java.security.AccessController.doPrivileged(Native Method)    at javax.security.auth.Subject.doAs(Subject.java:415)    at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1628)    at org.apache.hadoop.mapred.JobClient.submitJobInternal(JobClient.java:557)    at org.apache.hadoop.mapred.JobClient.submitJob(JobClient.java:548)    at org.apache.hadoop.mapred.JobClient.runJob(JobClient.java:833)    at com.zongtui.WordCount.main(WordCount.java:83)

1、改变输出路径。

2、删除重新建。

运行完成后看结果：