redhat linux rehl 5 hadoop 单机[伪分布式]安装

redhat linux rehl 5 hadoop 单机[伪分布式]安装
参考博客：
http://freewxy.iteye.com/blog/1027569
下载 解压 修改权限等暂时跳过.
ssh 免登录

[root@oplinux ~]# ssh-keygen -t rsa P ''
root@gen's password: 
Permission denied, please try again.
root@gen's password: 
Permission denied, please try again.
root@gen's password: 
Permission denied (publickey,gssapi-with-mic,password).
[root@oplinux .ssh]# vi /etc/ssh/sshd
//这个有错误 有时间在写.

//切换到hadoop目录
[root@oplinux ~]# cd /usr/local/hadoop
[root@oplinux hadoop]# ll
drwxrwxr-x 2 hehaibo hehaibo    4096 2010-08-17 bin
drwxrwxr-x 5 hehaibo hehaibo    4096 2010-08-17 c++
drwxr-xr-x 8 hehaibo hehaibo    4096 2010-08-17 common
drwxrwxr-x 2 hehaibo hehaibo    4096 2010-08-17 conf
-rw-rw-r-- 1 hehaibo hehaibo 1289953 2010-08-17 hadoop-common-0.21.0.jar
-rw-rw-r-- 1 hehaibo hehaibo  622276 2010-08-17 hadoop-common-test-0.21.0.jar
-rw-rw-r-- 1 hehaibo hehaibo  934881 2010-08-17 hadoop-hdfs-0.21.0.jar
-rw-rw-r-- 1 hehaibo hehaibo  613332 2010-08-17 hadoop-hdfs-0.21.0-sources.jar
-rw-rw-r-- 1 hehaibo hehaibo    6956 2010-08-17 hadoop-hdfs-ant-0.21.0.jar
-rw-rw-r-- 1 hehaibo hehaibo  688026 2010-08-17 hadoop-hdfs-test-0.21.0.jar
-rw-rw-r-- 1 hehaibo hehaibo  419671 2010-08-17 hadoop-hdfs-test-0.21.0-sources.jar
-rw-rw-r-- 1 hehaibo hehaibo 1747897 2010-08-17 hadoop-mapred-0.21.0.jar
-rw-rw-r-- 1 hehaibo hehaibo 1182309 2010-08-17 hadoop-mapred-0.21.0-sources.jar
-rw-rw-r-- 1 hehaibo hehaibo  252064 2010-08-17 hadoop-mapred-examples-0.21.0.jar
-rw-rw-r-- 1 hehaibo hehaibo 1492025 2010-08-17 hadoop-mapred-test-0.21.0.jar
-rw-rw-r-- 1 hehaibo hehaibo  298837 2010-08-17 hadoop-mapred-tools-0.21.0.jar
drwxr-xr-x 8 hehaibo hehaibo    4096 2010-08-17 hdfs
drwxrwxr-x 4 hehaibo hehaibo    4096 2010-08-17 lib
-rw-rw-r-- 1 hehaibo hehaibo   13366 2010-08-17 LICENSE.txt
drwxr-xr-x 9 hehaibo hehaibo    4096 2010-08-17 mapred
-rw-rw-r-- 1 hehaibo hehaibo     101 2010-08-17 NOTICE.txt
-rw-rw-r-- 1 hehaibo hehaibo    1366 2010-08-17 README.txt
drwxrwxr-x 8 hehaibo hehaibo    4096 2010-08-17 webapps
[root@oplinux hadoop]# vi conf/hadoop-env.sh
找到JAVA_HOME,设置Java环境变量
JAVA_HOME=/usr/local/jdk1.6.0_19
[root@oplinux hadoop]# vi conf/core-site.xml
    <configuration>  
     <property>  
      <name>fs.default.name</name>  
      <value>hdfs://localhost:9000</value>   
     </property>  
     <property>  
      <name>dfs.replication</name>   
      <value>1</value>   
     </property>  
     <property>  
      <name>hadoop.tmp.dir</name>  
      <value>/home/root/tmp</value>   
     </property>  
    </configuration> 
	
[root@oplinux hadoop]# vi conf/mapred-site.xml
    <configuration>  
     <property>   
      <name>mapred.job.tracker</name>  
      <value>localhost:9001</value>   
     </property>  
    </configuration>  
[root@oplinux hadoop]# cd bin/
//查看bin目录下的内容
[root@oplinux bin]# ll
总计 160
-rwxr-xr-x 1 hehaibo hehaibo 4131 2010-08-17 hadoop
-rwxr-xr-x 1 hehaibo hehaibo 8658 2010-08-17 hadoop-config.sh
-rwxr-xr-x 1 hehaibo hehaibo 3841 2010-08-17 hadoop-daemon.sh
-rwxr-xr-x 1 hehaibo hehaibo 1242 2010-08-17 hadoop-daemons.sh
-rwxr-xr-x 1 hehaibo hehaibo 4130 2010-08-17 hdfs
-rwxr-xr-x 1 hehaibo hehaibo 1201 2010-08-17 hdfs-config.sh
-rwxr-xr-x 1 hehaibo hehaibo 3387 2010-08-17 mapred
-rwxr-xr-x 1 hehaibo hehaibo 1207 2010-08-17 mapred-config.sh
-rwxr-xr-x 1 hehaibo hehaibo 2720 2010-08-17 rcc
-rwxr-xr-x 1 hehaibo hehaibo 2058 2010-08-17 slaves.sh
-rwxr-xr-x 1 hehaibo hehaibo 1367 2010-08-17 start-all.sh
-rwxr-xr-x 1 hehaibo hehaibo 1018 2010-08-17 start-balancer.sh
-rwxr-xr-x 1 hehaibo hehaibo 1778 2010-08-17 start-dfs.sh
-rwxr-xr-x 1 hehaibo hehaibo 1255 2010-08-17 start-mapred.sh
-rwxr-xr-x 1 hehaibo hehaibo 1359 2010-08-17 stop-all.sh
-rwxr-xr-x 1 hehaibo hehaibo 1069 2010-08-17 stop-balancer.sh
-rwxr-xr-x 1 hehaibo hehaibo 1277 2010-08-17 stop-dfs.sh
-rwxr-xr-x 1 hehaibo hehaibo 1163 2010-08-17 stop-mapred.sh

//格式化namenode[为什么要格式化,有待研究]
[root@oplinux bin]# sh hadoop namenode -format
DEPRECATED: Use of this script to execute hdfs command is deprecated.
Instead use the hdfs command for it.

11/08/13 10:56:18 INFO namenode.NameNode: STARTUP_MSG: 
/************************************************************
STARTUP_MSG: Starting NameNode
STARTUP_MSG:   host = oplinux.hehaibo.com/127.0.0.1
STARTUP_MSG:   args = [-format]
STARTUP_MSG:   version = 0.21.0
STARTUP_MSG:   classpath = /usr/local/hadoop/bin/../conf:/usr/local/jdk1.6.0_19/lib/tools.jar:/usr/local/hadoop/bin/..:/usr/local/hadoop/bin/../hadoop-common-0.21.0.jar:/usr/local/hadoop/bin/../hadoop-common-test-0.21.0.jar:/usr/local/hadoop/bin/../hadoop-hdfs-0.21.0.jar:/usr/local/hadoop/bin/../hadoop-hdfs-0.21.0-sources.jar:/usr/local/hadoop/bin/../hadoop-hdfs-ant-0.21.0.jar:/usr/local/hadoop/bin/../hadoop-hdfs-test-0.21.0.jar:/usr/local/hadoop/bin/../hadoop-hdfs-test-0.21.0-sources.jar:/usr/local/hadoop/bin/../hadoop-mapred-0.21.0.jar:/usr/local/hadoop/bin/../hadoop-mapred-0.21.0-sources.jar:/usr/local/hadoop/bin/../hadoop-mapred-examples-0.21.0.jar:/usr/local/hadoop/bin/../hadoop-mapred-test-0.21.0.jar:/usr/local/hadoop/bin/../hadoop-mapred-tools-0.21.0.jar:/usr/local/hadoop/bin/../lib/ant-1.6.5.jar:/usr/local/hadoop/bin/../lib/asm-3.2.jar:/usr/local/hadoop/bin/../lib/aspectjrt-1.6.5.jar:/usr/local/hadoop/bin/../lib/aspectjtools-1.6.5.jar:/usr/local/hadoop/bin/../lib/avro-1.3.2.jar:/usr/local/hadoop/bin/../lib/commons-cli-1.2.jar:/usr/local/hadoop/bin/../lib/commons-codec-1.4.jar:/usr/local/hadoop/bin/../lib/commons-el-1.0.jar:/usr/local/hadoop/bin/../lib/commons-httpclient-3.1.jar:/usr/local/hadoop/bin/../lib/commons-lang-2.5.jar:/usr/local/hadoop/bin/../lib/commons-logging-1.1.1.jar:/usr/local/hadoop/bin/../lib/commons-logging-api-1.1.jar:/usr/local/hadoop/bin/../lib/commons-net-1.4.1.jar:/usr/local/hadoop/bin/../lib/core-3.1.1.jar:/usr/local/hadoop/bin/../lib/ftplet-api-1.0.0.jar:/usr/local/hadoop/bin/../lib/ftpserver-core-1.0.0.jar:/usr/local/hadoop/bin/../lib/ftpserver-deprecated-1.0.0-M2.jar:/usr/local/hadoop/bin/../lib/hsqldb-1.8.0.10.jar:/usr/local/hadoop/bin/../lib/jackson-core-asl-1.4.2.jar:/usr/local/hadoop/bin/../lib/jackson-mapper-asl-1.4.2.jar:/usr/local/hadoop/bin/../lib/jasper-compiler-5.5.12.jar:/usr/local/hadoop/bin/../lib/jasper-runtime-5.5.12.jar:/usr/local/hadoop/bin/../lib/jdiff-1.0.9.jar:/usr/local/hadoop/bin/../lib/jets3t-0.7.1.jar:/usr/local/hadoop/bin/../lib/jetty-6.1.14.jar:/usr/local/hadoop/bin/../lib/jetty-util-6.1.14.jar:/usr/local/hadoop/bin/../lib/jsp-2.1-6.1.14.jar:/usr/local/hadoop/bin/../lib/jsp-api-2.1-6.1.14.jar:/usr/local/hadoop/bin/../lib/junit-4.8.1.jar:/usr/local/hadoop/bin/../lib/kfs-0.3.jar:/usr/local/hadoop/bin/../lib/log4j-1.2.15.jar:/usr/local/hadoop/bin/../lib/mina-core-2.0.0-M5.jar:/usr/local/hadoop/bin/../lib/mockito-all-1.8.2.jar:/usr/local/hadoop/bin/../lib/oro-2.0.8.jar:/usr/local/hadoop/bin/../lib/paranamer-2.2.jar:/usr/local/hadoop/bin/../lib/paranamer-ant-2.2.jar:/usr/local/hadoop/bin/../lib/paranamer-generator-2.2.jar:/usr/local/hadoop/bin/../lib/qdox-1.10.1.jar:/usr/local/hadoop/bin/../lib/servlet-api-2.5-6.1.14.jar:/usr/local/hadoop/bin/../lib/slf4j-api-1.5.11.jar:/usr/local/hadoop/bin/../lib/slf4j-log4j12-1.5.11.jar:/usr/local/hadoop/bin/../lib/xmlenc-0.52.jar:/usr/local/hadoop/bin/../lib/jsp-2.1/*.jar:/usr/local/hadoop/hdfs/bin/../conf:/usr/local/hadoop/hdfs/bin/../hadoop-hdfs-*.jar:/usr/local/hadoop/hdfs/bin/../lib/*.jar:/usr/local/hadoop/bin/../mapred/conf:/usr/local/hadoop/bin/../mapred/hadoop-mapred-*.jar:/usr/local/hadoop/bin/../mapred/lib/*.jar:/usr/local/hadoop/hdfs/bin/../hadoop-hdfs-*.jar:/usr/local/hadoop/hdfs/bin/../lib/*.jar
STARTUP_MSG:   build = 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
************************************************************/
11/08/13 10:56:19 INFO namenode.FSNamesystem: defaultReplication = 3
11/08/13 10:56:19 INFO namenode.FSNamesystem: maxReplication = 512
11/08/13 10:56:19 INFO namenode.FSNamesystem: minReplication = 1
11/08/13 10:56:19 INFO namenode.FSNamesystem: maxReplicationStreams = 2
11/08/13 10:56:19 INFO namenode.FSNamesystem: shouldCheckForEnoughRacks = false
11/08/13 10:56:19 INFO security.Groups: Group mapping impl=org.apache.hadoop.security.ShellBasedUnixGroupsMapping; cacheTimeout=300000
11/08/13 10:56:20 INFO namenode.FSNamesystem: fsOwner=root
11/08/13 10:56:20 INFO namenode.FSNamesystem: supergroup=supergroup
11/08/13 10:56:20 INFO namenode.FSNamesystem: isPermissionEnabled=true
11/08/13 10:56:20 INFO namenode.FSNamesystem: isAccessTokenEnabled=false accessKeyUpdateInterval=0 min(s), accessTokenLifetime=0 min(s)
11/08/13 10:56:21 INFO common.Storage: Image file of size 110 saved in 0 seconds.
11/08/13 10:56:21 INFO common.Storage: Storage directory /home/root/tmp/dfs/name has been successfully formatted.
11/08/13 10:56:21 INFO namenode.NameNode: SHUTDOWN_MSG: 
/************************************************************
SHUTDOWN_MSG: Shutting down NameNode at oplinux.hehaibo.com/127.0.0.1
************************************************************/

//停止hadoop
[root@oplinux bin]# sh stop-all.sh
This script is Deprecated. Instead use stop-dfs.sh and stop-mapred.sh
no namenode to stop
localhost: no datanode to stop
localhost: no secondarynamenode to stop
no jobtracker to stop
localhost: no tasktracker to stop
[root@oplinux bin]# sh start-all.sh
This script is Deprecated. Instead use start-dfs.sh and start-mapred.sh
starting namenode, logging to /usr/local/hadoop/bin/../logs/hadoop-root-namenode-oplinux.hehaibo.com.out
localhost: starting datanode, logging to /usr/local/hadoop/bin/../logs/hadoop-root-datanode-oplinux.hehaibo.com.out
localhost: starting secondarynamenode, logging to /usr/local/hadoop/bin/../logs/hadoop-root-secondarynamenode-oplinux.hehaibo.com.out
starting jobtracker, logging to /usr/local/hadoop/bin/../logs/hadoop-root-jobtracker-oplinux.hehaibo.com.out
localhost: starting tasktracker, logging to /usr/local/hadoop/bin/../logs/hadoop-root-tasktracker-oplinux.hehaibo.com.out
[root@oplinux bin]# 
//启动hadoop
[root@oplinux bin]# sh start-all.sh
This script is Deprecated. Instead use start-dfs.sh and start-mapred.sh
starting namenode, logging to /usr/local/hadoop/bin/../logs/hadoop-root-namenode-oplinux.hehaibo.com.out
localhost: starting datanode, logging to /usr/local/hadoop/bin/../logs/hadoop-root-datanode-oplinux.hehaibo.com.out
localhost: starting secondarynamenode, logging to /usr/local/hadoop/bin/../logs/hadoop-root-secondarynamenode-oplinux.hehaibo.com.out
starting jobtracker, logging to /usr/local/hadoop/bin/../logs/hadoop-root-jobtracker-oplinux.hehaibo.com.out
localhost: starting tasktracker, logging to /usr/local/hadoop/bin/../logs/hadoop-root-tasktracker-oplinux.hehaibo.com.out
//验证启动是否成功
[root@oplinux hadoop]# jps
5333 TaskTracker
6035 Jps
4801 NameNode
5190 JobTracker
5078 SecondaryNameNode
4940 DataNode
[root@oplinux hadoop]# jps
5333 TaskTracker
6068 Jps
4801 NameNode
5190 JobTracker
5078 SecondaryNameNode
4940 DataNode

//创建一份测试文件 如：/home/root/hadooptest.txt
//我的dfs文件目录为/user/root [linux目录上不会存在，这个应该是hadoop的文件目录]
/**
* dfs 文件操作命令
  //创建目录
  dfs -mkdir firsttest //实际上会在hadoop /user/root上创建/user/root/firsttest
  dfs -ls 查看文件命令
  dfs -rm 删除目录
*/
//切换目录
[root@oplinux bin]# cd ../
//执行一个例子
//先创建文件 /home/root/hadooptest.txt 文件内容随便输入些英文单词
我们将文件上传到hadoop 文件目录firsttest中.
[root@oplinux hadoop]# sh hadoop dfs -copyFromLocal /home/root/hadooptest.txt firsttest
sh: hadoop: 没有那个文件或目录
//注意这个错误，是firsttest目录不存在
//执行下面命令创建它
[root@oplinux hadoop]# bin/hadoop dfs -mkdir firsttest
DEPRECATED: Use of this script to execute hdfs command is deprecated.
Instead use the hdfs command for it.

11/08/13 12:11:52 INFO security.Groups: Group mapping impl=org.apache.hadoop.security.ShellBasedUnixGroupsMapping; cacheTimeout=300000
11/08/13 12:11:52 WARN conf.Configuration: mapred.task.id is deprecated. Instead, use mapreduce.task.attempt.id

//查看创建的目录
[root@oplinux hadoop]# bin/hadoop dfs -ls
DEPRECATED: Use of this script to execute hdfs command is deprecated.
Instead use the hdfs command for it.

11/08/13 12:12:46 INFO security.Groups: Group mapping impl=org.apache.hadoop.security.ShellBasedUnixGroupsMapping; cacheTimeout=300000
11/08/13 12:12:46 WARN conf.Configuration: mapred.task.id is deprecated. Instead, use mapreduce.task.attempt.id
Found 2 items
drwxr-xr-x   - root supergroup          0 2011-08-13 12:11 /user/root/firsttest
[root@oplinux hadoop]# 

//我们再执行wordcount 将执行的结果保存到result目录下
[root@oplinux hadoop]# bin/hadoop jar hadoop-mapred-examples-0.21.0.jar wordcount firsttestttttt result
11/08/13 11:50:49 INFO security.Groups: Group mapping impl=org.apache.hadoop.security.ShellBasedUnixGroupsMapping; cacheTimeout=300000
11/08/13 11:50:50 WARN conf.Configuration: mapred.task.id is deprecated. Instead, use mapreduce.task.attempt.id
11/08/13 11:50:50 WARN mapreduce.JobSubmitter: Use GenericOptionsParser for parsing the arguments. Applications should implement Tool for the same.
11/08/13 11:50:50 INFO mapreduce.JobSubmitter: Cleaning up the staging area hdfs://localhost:9000/home/root/tmp/mapred/staging/root/.staging/job_201108131105_0006
org.apache.hadoop.mapreduce.lib.input.InvalidInputException: Input path does not exist: hdfs://localhost:9000/user/root/firsttestttttt
        at org.apache.hadoop.mapreduce.lib.input.FileInputFormat.listStatus(FileInputFormat.java:245)
        at org.apache.hadoop.mapreduce.lib.input.FileInputFormat.getSplits(FileInputFormat.java:271)
        at org.apache.hadoop.mapreduce.JobSubmitter.writeNewSplits(JobSubmitter.java:401)
        at org.apache.hadoop.mapreduce.JobSubmitter.writeSplits(JobSubmitter.java:418)
        at org.apache.hadoop.mapreduce.JobSubmitter.submitJobInternal(JobSubmitter.java:338)
        at org.apache.hadoop.mapreduce.Job.submit(Job.java:960)
        at org.apache.hadoop.mapreduce.Job.waitForCompletion(Job.java:976)
        at org.apache.hadoop.examples.WordCount.main(WordCount.java:84)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.apache.hadoop.util.ProgramDriver$ProgramDescription.invoke(ProgramDriver.java:72)
        at org.apache.hadoop.util.ProgramDriver.driver(ProgramDriver.java:144)
        at org.apache.hadoop.examples.ExampleDriver.main(ExampleDriver.java:68)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.apache.hadoop.util.RunJar.main(RunJar.java:192)

		
//出现错误, Input path does not exist: hdfs://localhost:9000/user/root/tmp/firsttestttttt
//仔细检查，发现是firsttestttttt 这个目录不存在，是因为你没有创建firsttest 所以不存在，创建了就ok了
//正确的结果
[root@oplinux hadoop]# bin/hadoop jar hadoop-mapred-examples-0.21.0.jar wordcount firsttest result
11/08/13 13:56:11 INFO security.Groups: Group mapping impl=org.apache.hadoop.security.ShellBasedUnixGroupsMapping; cacheTimeout=300000
11/08/13 13:56:12 WARN conf.Configuration: mapred.task.id is deprecated. Instead, use mapreduce.task.attempt.id
11/08/13 13:56:12 WARN mapreduce.JobSubmitter: Use GenericOptionsParser for parsing the arguments. Applications should implement Tool for the same.
11/08/13 13:56:13 INFO input.FileInputFormat: Total input paths to process : 1
11/08/13 13:56:14 WARN conf.Configuration: mapred.map.tasks is deprecated. Instead, use mapreduce.job.maps
11/08/13 13:56:14 INFO mapreduce.JobSubmitter: number of splits:1
11/08/13 13:56:14 INFO mapreduce.JobSubmitter: adding the following namenodes' delegation tokens:null
11/08/13 13:56:15 INFO mapreduce.Job: Running job: job_201108131105_0011
11/08/13 13:56:16 INFO mapreduce.Job:  map 0% reduce 0%
11/08/13 13:56:43 INFO mapreduce.Job:  map 100% reduce 0%
11/08/13 13:57:04 INFO mapreduce.Job:  map 100% reduce 100%
11/08/13 13:57:06 INFO mapreduce.Job: Job complete: job_201108131105_0011
11/08/13 13:57:06 INFO mapreduce.Job: Counters: 33
        FileInputFormatCounters
                BYTES_READ=141
        FileSystemCounters
                FILE_BYTES_READ=284
                FILE_BYTES_WRITTEN=600
                HDFS_BYTES_READ=262
                HDFS_BYTES_WRITTEN=178
        Shuffle Errors
                BAD_ID=0
                CONNECTION=0
                IO_ERROR=0
                WRONG_LENGTH=0
                WRONG_MAP=0
                WRONG_REDUCE=0
        Job Counters
                Data-local map tasks=1
                Total time spent by all maps waiting after reserving slots (ms)=0
                Total time spent by all reduces waiting after reserving slots (ms)=0
                SLOTS_MILLIS_MAPS=22524
                SLOTS_MILLIS_REDUCES=18291
                Launched map tasks=1
                Launched reduce tasks=1
        Map-Reduce Framework
                Combine input records=28
                Combine output records=25
                Failed Shuffles=0
                GC time elapsed (ms)=404
                Map input records=4
                Map output bytes=253
                Map output records=28
                Merged Map outputs=1
                Reduce input groups=25
                Reduce input records=25
                Reduce output records=25
                Reduce shuffle bytes=284
                Shuffled Maps =1
                Spilled Records=50
                SPLIT_RAW_BYTES=121 
				
				
/**
/////这个错误提示Output directory result already exists  因为之前执行过，可以先删除result目录 执行命令 bin/hadoop dfs -rm result
[root@oplinux hadoop]# bin/hadoop jar hadoop-mapred-examples-0.21.0.jar wordcount firsttest result
11/08/13 12:17:24 INFO security.Groups: Group mapping impl=org.apache.hadoop.security.ShellBasedUnixGroupsMapping; cacheTimeout=300000
11/08/13 12:17:25 WARN conf.Configuration: mapred.task.id is deprecated. Instead, use mapreduce.task.attempt.id
11/08/13 12:17:25 WARN mapreduce.JobSubmitter: Use GenericOptionsParser for parsing the arguments. Applications should implement Tool for the same.
11/08/13 12:17:25 INFO mapreduce.JobSubmitter: Cleaning up the staging area hdfs://localhost:9000/home/root/tmp/mapred/staging/root/.staging/job_201108131105_0009
org.apache.hadoop.fs.FileAlreadyExistsException: Output directory result already exists
        at org.apache.hadoop.mapreduce.lib.output.FileOutputFormat.checkOutputSpecs(FileOutputFormat.java:140)
        at org.apache.hadoop.mapreduce.JobSubmitter.checkSpecs(JobSubmitter.java:373)
        at org.apache.hadoop.mapreduce.JobSubmitter.submitJobInternal(JobSubmitter.java:334)
        at org.apache.hadoop.mapreduce.Job.submit(Job.java:960)
        at org.apache.hadoop.mapreduce.Job.waitForCompletion(Job.java:976)
        at org.apache.hadoop.examples.WordCount.main(WordCount.java:84)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:59
*/				
//我们查看执行结果后的目录
[root@oplinux hadoop]# bin/hadoop dfs -ls
DEPRECATED: Use of this script to execute hdfs command is deprecated.
Instead use the hdfs command for it.

11/08/13 12:12:46 INFO security.Groups: Group mapping impl=org.apache.hadoop.security.ShellBasedUnixGroupsMapping; cacheTimeout=300000
11/08/13 12:12:46 WARN conf.Configuration: mapred.task.id is deprecated. Instead, use mapreduce.task.attempt.id
Found 2 items
//执行计算的目录
drwxr-xr-x   - root supergroup          0 2011-08-13 12:11 /user/root/firsttest
//输出结果的目录
drwxr-xr-x   - root supergroup          0 2011-08-13 11:52 /user/root/result

[root@oplinux hadoop]# 
/////查看结果

//查看执行后result目录下有哪些内容
[root@oplinux hadoop]# bin/hadoop dfs -ls result
DEPRECATED: Use of this script to execute hdfs command is deprecated.
Instead use the hdfs command for it.

11/08/13 14:06:23 INFO security.Groups: Group mapping impl=org.apache.hadoop.security.ShellBasedUnixGroupsMapping; cacheTimeout=300000
11/08/13 14:06:23 WARN conf.Configuration: mapred.task.id is deprecated. Instead, use mapreduce.task.attempt.id
Found 2 items
-rw-r--r--   3 root supergroup          0 2011-08-13 13:57 /user/root/result/_SUCCESS
-rw-r--r--   3 root supergroup        178 2011-08-13 13:56 /user/root/result/part-r-00000 

//查看文件内容
[root@oplinux hadoop]# bin/hadoop dfs -cat result/part-r-00000
DEPRECATED: Use of this script to execute hdfs command is deprecated.
Instead use the hdfs command for it.

11/08/13 14:08:34 INFO security.Groups: Group mapping impl=org.apache.hadoop.security.ShellBasedUnixGroupsMapping; cacheTimeout=300000
11/08/13 14:08:34 WARN conf.Configuration: mapred.task.id is deprecated. Instead, use mapreduce.task.attempt.id
.       1
I       1
a       1
am      1
case    1
do      1
everything      1
example 1
hadoop  2
happy   1
hehaibo 1
hello   1
if      1
is      3
jsut    1
linux   1
play    1
possible        1
sunday  1
this    1
to      1
today   1
with    1
yes     1
you     1
[root@oplinux hadoop]# 

暂时告一段落。