本文描述如何设置一个单一节点的 Hadoop 安装，以便您可以快速执行简单的操作，使用 Hadoop MapReduce 和 Hadoop 分布式文件系统 (HDFS)。
参考官方文档：Hadoop MapReduce Next Generation - Setting up a Single Node Cluster.
Hadoop版本：Apache Hadoop 2.5.1
系统版本：CentOS 6.5，内核（uname -r）：2.6.32-431.el6.x86_64
支持的系统平台
GNU/Linux 作为开发和生产的平台，毫无疑问。Windows 也是受支持的平台，但是以下步骤仅用于 Linux。
依赖的软件
在Linux系统上安装所需要的软件包
1、JAVA（JDK）必须安装，推荐的版本请参考Hadoop JAVA Version，我这里安装的是1.7。
2、ssh 必须安装，必须运行 sshd 才能使用管理远程 Hadoop 守护程序的 Hadoop 脚本。
安装依赖的软件
如果您的系统没有所需的软件，您将需要安装它。
例如在Ubuntu Linux上使用以下命令:
$ sudo apt-get install ssh $ sudo apt-get install rsync
CentOS应该是即使是最小安装也带了ssh（Secure Shell），刚开始我给弄混了，以为是JAVA的SSH（Spring + Struts +Hibernate），汗！
安装JDK，参考：CentOS下安装JDK7
就不多说了，上一篇下过了。链接：Hadoop学习笔记（一）从官网下载安装包
解压文件hadoop-2.5.1.tar.gz，执行：tar xvf hadoop-2.5.1.tar.gz，会将文件解压到hadoop-2.5.1目录下；
切换目录:cd hadoop-2.5.1/etc/hadoop/
编辑“hadoop-env.sh”文件，添加参考定义；
vi hadoop-env.sh
个人觉得比较好的习惯是编辑文件之前先做个备份（cp hadoop-env.sh hadoop-env.sh.bak）；
找到以下位置：
# The java implementation to use.
export JAVA_HOME={JAVA_HOME}将其改为：# The java implementation to use. export JAVA_HOME=/usr/java/latest在下面再添加一句：
# Assuming your installation directory is /usr/local/hadoop export HADOOP_PREFIX=/usr/local/hadoop保存并退出，ESC,:wq
切换目录（cd ../..），返回“/opt/hadoop-2.5.1”；
尝试执行以下命令：
./bin/hadoop
这将显示 hadoop 脚本的使用文档，输出如下：
Usage: hadoop [--config confdir] COMMAND
where COMMAND is one of:
fs run a generic filesystem user client
version print the version
jar <jar> run a jar file
checknative [-a|-h] check native hadoop and compression libraries availability
distcp <srcurl> <desturl> copy file or directories recursively
archive -archiveName NAME -p <parent path> <src>* <dest> 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.默认情况下，Hadoop 被配置为运行在非分布式模式下，作为一个单一的 Java 进程。这比较适合用于调试。
下面的示例复制要使用作为输入的解压缩的 conf 目录，然后查找并显示给定正则表达式的每一场比赛。输出被写入给定的输出目录。
$ mkdir input $ cp etc/hadoop/*.xml input $ bin/hadoop jar share/hadoop/mapreduce/hadoop-mapreduce-examples-2.5.1.jar grep input output ‘dfs[a-z.]+‘ $ cat output/*
执行“bin/hadoop jar share/hadoop/mapreduce/hadoop-mapreduce-examples-2.5.1.jar grep input output ‘dfs[a-z.]+‘”时
却出现错误：Error: Could not find or load main class org.apache.hadoop.util.RunJar
此问题只在Stack Overflow上见到
但是也没能找到解决的办法；还是自己摸索吧！
解决步骤：
刚刚备份的“hadoop-env.sh”文件现在用上了，还原它。
再执行“bin/hadoop jar share/hadoop/mapreduce/hadoop-mapreduce-examples-2.5.1.jar grep input output ‘dfs[a-z.]+‘”，
提示：
./bin/hadoop: line 133: /usr/java/jdk1.7.0/bin/java: No such file or directory ./bin/hadoop: line 133: exec: /usr/java/jdk1.7.0/bin/java: cannot execute: No such file or directory按提示应该还是JAVA（JDK）的安装的问题，我安装JDK的时候只执行到
rpm -ivh /目录/jdk-7-linux-x64.rpm再没执行其它操作，将后续的步骤执行完成后，再执行“bin/hadoop jar share/hadoop/mapreduce/hadoop-mapreduce-examples-2.5.1.jar grep input output ‘dfs[a-z.]+‘”，
输出：
14/10/07 03:35:57 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable 14/10/07 03:35:58 INFO Configuration.deprecation: session.id is deprecated. Instead, use dfs.metrics.session-id 14/10/07 03:35:58 INFO jvm.JvmMetrics: Initializing JVM Metrics with processName=JobTracker, sessionId= 14/10/07 03:35:59 WARN mapreduce.JobSubmitter: No job jar file set. User classes may not be found. See Job or Job#setJar(String). 14/10/07 03:35:59 INFO input.FileInputFormat: Total input paths to process : 6 14/10/07 03:35:59 INFO mapreduce.JobSubmitter: number of splits:6 14/10/07 03:36:00 INFO mapreduce.JobSubmitter: Submitting tokens for job: job_local1185570365_0001 14/10/07 03:36:00 WARN conf.Configuration: file:/tmp/hadoop-root/mapred/staging/root1185570365/.staging/job_local1185570365_0001/job.xml:an attempt to override final parameter: mapreduce.job.end-notification.max.retry.interval; Ignoring. 14/10/07 03:36:01 WARN conf.Configuration: file:/tmp/hadoop-root/mapred/staging/root1185570365/.staging/job_local1185570365_0001/job.xml:an attempt to override final parameter: mapreduce.job.end-notification.max.attempts; Ignoring. 14/10/07 03:36:01 WARN conf.Configuration: file:/tmp/hadoop-root/mapred/local/localRunner/root/job_local1185570365_0001/job_local1185570365_0001.xml:an attempt to override final parameter: mapreduce.job.end-notification.max.retry.interval; Ignoring. 14/10/07 03:36:01 WARN conf.Configuration: file:/tmp/hadoop-root/mapred/local/localRunner/root/job_local1185570365_0001/job_local1185570365_0001.xml:an attempt to override final parameter: mapreduce.job.end-notification.max.attempts; Ignoring. 14/10/07 03:36:01 INFO mapreduce.Job: The url to track the job: http://localhost:8080/ 14/10/07 03:36:01 INFO mapreduce.Job: Running job: job_local1185570365_0001 14/10/07 03:36:01 INFO mapred.LocalJobRunner: OutputCommitter set in config null 14/10/07 03:36:01 INFO mapred.LocalJobRunner: OutputCommitter is org.apache.hadoop.mapreduce.lib.output.FileOutputCommitter 14/10/07 03:36:02 INFO mapred.LocalJobRunner: Waiting for map tasks 14/10/07 03:36:02 INFO mapred.LocalJobRunner: Starting task: attempt_local1185570365_0001_m_000000_0 14/10/07 03:36:02 INFO mapred.Task: Using ResourceCalculatorProcessTree : [ ] 14/10/07 03:36:02 INFO mapred.MapTask: Processing split: file:/opt/hadoop-2.5.1/input/hadoop-policy.xml:0+9201 14/10/07 03:36:02 INFO mapred.MapTask: Map output collector class = org.apache.hadoop.mapred.MapTask$MapOutputBuffer 14/10/07 03:36:02 INFO mapred.MapTask: (EQUATOR) 0 kvi 26214396(104857584) 14/10/07 03:36:02 INFO mapred.MapTask: mapreduce.task.io.sort.mb: 100 14/10/07 03:36:02 INFO mapred.MapTask: soft limit at 83886080 14/10/07 03:36:02 INFO mapred.MapTask: bufstart = 0; bufvoid = 104857600 14/10/07 03:36:02 INFO mapred.MapTask: kvstart = 26214396; length = 6553600 14/10/07 03:36:02 INFO mapred.LocalJobRunner: 14/10/07 03:36:02 INFO mapred.MapTask: Starting flush of map output 14/10/07 03:36:02 INFO mapred.MapTask: Spilling map output 14/10/07 03:36:02 INFO mapred.MapTask: bufstart = 0; bufend = 17; bufvoid = 104857600 14/10/07 03:36:02 INFO mapred.MapTask: kvstart = 26214396(104857584); kvend = 26214396(104857584); length = 1/6553600 14/10/07 03:36:02 INFO mapreduce.Job: Job job_local1185570365_0001 running in uber mode : false 14/10/07 03:36:02 INFO mapred.MapTask: Finished spill 0 14/10/07 03:36:02 INFO mapreduce.Job: map 0% reduce 0% 14/10/07 03:36:02 INFO mapred.Task: Task:attempt_local1185570365_0001_m_000000_0 is done. And is in the process of committing 14/10/07 03:36:02 INFO mapred.LocalJobRunner: map 14/10/07 03:36:02 INFO mapred.Task: Task ‘attempt_local1185570365_0001_m_000000_0‘ done. 14/10/07 03:36:02 INFO mapred.LocalJobRunner: Finishing task: attempt_local1185570365_0001_m_000000_0 14/10/07 03:36:02 INFO mapred.LocalJobRunner: Starting task: attempt_local1185570365_0001_m_000001_0 14/10/07 03:36:02 INFO mapred.Task: Using ResourceCalculatorProcessTree : [ ] 14/10/07 03:36:02 INFO mapred.MapTask: Processing split: file:/opt/hadoop-2.5.1/input/capacity-scheduler.xml:0+3589 14/10/07 03:36:02 INFO mapred.MapTask: Map output collector class = org.apache.hadoop.mapred.MapTask$MapOutputBuffer 14/10/07 03:36:02 INFO mapred.MapTask: (EQUATOR) 0 kvi 26214396(104857584) 14/10/07 03:36:02 INFO mapred.MapTask: mapreduce.task.io.sort.mb: 100 14/10/07 03:36:02 INFO mapred.MapTask: soft limit at 83886080 14/10/07 03:36:02 INFO mapred.MapTask: bufstart = 0; bufvoid = 104857600 14/10/07 03:36:02 INFO mapred.MapTask: kvstart = 26214396; length = 6553600 14/10/07 03:36:02 INFO mapred.LocalJobRunner: 14/10/07 03:36:02 INFO mapred.MapTask: Starting flush of map output 14/10/07 03:36:02 INFO mapred.Task: Task:attempt_local1185570365_0001_m_000001_0 is done. And is in the process of committing 14/10/07 03:36:02 INFO mapred.LocalJobRunner: map 14/10/07 03:36:02 INFO mapred.Task: Task ‘attempt_local1185570365_0001_m_000001_0‘ done. 14/10/07 03:36:02 INFO mapred.LocalJobRunner: Finishing task: attempt_local1185570365_0001_m_000001_0 14/10/07 03:36:02 INFO mapred.LocalJobRunner: Starting task: attempt_local1185570365_0001_m_000002_0 14/10/07 03:36:02 INFO mapred.Task: Using ResourceCalculatorProcessTree : [ ] 14/10/07 03:36:02 INFO mapred.MapTask: Processing split: file:/opt/hadoop-2.5.1/input/hdfs-site.xml:0+775 14/10/07 03:36:02 INFO mapred.MapTask: Map output collector class = org.apache.hadoop.mapred.MapTask$MapOutputBuffer 14/10/07 03:36:03 INFO mapred.MapTask: (EQUATOR) 0 kvi 26214396(104857584) 14/10/07 03:36:03 INFO mapred.MapTask: mapreduce.task.io.sort.mb: 100 14/10/07 03:36:03 INFO mapred.MapTask: soft limit at 83886080 14/10/07 03:36:03 INFO mapred.MapTask: bufstart = 0; bufvoid = 104857600 14/10/07 03:36:03 INFO mapred.MapTask: kvstart = 26214396; length = 6553600 14/10/07 03:36:03 INFO mapred.LocalJobRunner: 14/10/07 03:36:03 INFO mapred.MapTask: Starting flush of map output 14/10/07 03:36:03 INFO mapred.Task: Task:attempt_local1185570365_0001_m_000002_0 is done. And is in the process of committing 14/10/07 03:36:03 INFO mapred.LocalJobRunner: map 14/10/07 03:36:03 INFO mapred.Task: Task ‘attempt_local1185570365_0001_m_000002_0‘ done. 14/10/07 03:36:03 INFO mapred.LocalJobRunner: Finishing task: attempt_local1185570365_0001_m_000002_0 14/10/07 03:36:03 INFO mapred.LocalJobRunner: Starting task: attempt_local1185570365_0001_m_000003_0 14/10/07 03:36:03 INFO mapred.Task: Using ResourceCalculatorProcessTree : [ ] 14/10/07 03:36:03 INFO mapred.MapTask: Processing split: file:/opt/hadoop-2.5.1/input/core-site.xml:0+774 14/10/07 03:36:03 INFO mapred.MapTask: Map output collector class = org.apache.hadoop.mapred.MapTask$MapOutputBuffer 14/10/07 03:36:03 INFO mapred.MapTask: (EQUATOR) 0 kvi 26214396(104857584) 14/10/07 03:36:03 INFO mapred.MapTask: mapreduce.task.io.sort.mb: 100 14/10/07 03:36:03 INFO mapred.MapTask: soft limit at 83886080 14/10/07 03:36:03 INFO mapred.MapTask: bufstart = 0; bufvoid = 104857600 14/10/07 03:36:03 INFO mapred.MapTask: kvstart = 26214396; length = 6553600 14/10/07 03:36:03 INFO mapred.LocalJobRunner: 14/10/07 03:36:03 INFO mapred.MapTask: Starting flush of map output 14/10/07 03:36:03 INFO mapred.Task: Task:attempt_local1185570365_0001_m_000003_0 is done. And is in the process of committing 14/10/07 03:36:03 INFO mapred.LocalJobRunner: map 14/10/07 03:36:03 INFO mapred.Task: Task ‘attempt_local1185570365_0001_m_000003_0‘ done. 14/10/07 03:36:03 INFO mapred.LocalJobRunner: Finishing task: attempt_local1185570365_0001_m_000003_0 14/10/07 03:36:03 INFO mapred.LocalJobRunner: Starting task: attempt_local1185570365_0001_m_000004_0 14/10/07 03:36:03 INFO mapred.Task: Using ResourceCalculatorProcessTree : [ ] 14/10/07 03:36:03 INFO mapred.MapTask: Processing split: file:/opt/hadoop-2.5.1/input/yarn-site.xml:0+690 14/10/07 03:36:03 INFO mapred.MapTask: Map output collector class = org.apache.hadoop.mapred.MapTask$MapOutputBuffer 14/10/07 03:36:03 INFO mapred.MapTask: (EQUATOR) 0 kvi 26214396(104857584) 14/10/07 03:36:03 INFO mapred.MapTask: mapreduce.task.io.sort.mb: 100 14/10/07 03:36:03 INFO mapred.MapTask: soft limit at 83886080 14/10/07 03:36:03 INFO mapred.MapTask: bufstart = 0; bufvoid = 104857600 14/10/07 03:36:03 INFO mapred.MapTask: kvstart = 26214396; length = 6553600 14/10/07 03:36:03 INFO mapred.LocalJobRunner: 14/10/07 03:36:03 INFO mapred.MapTask: Starting flush of map output 14/10/07 03:36:03 INFO mapred.Task: Task:attempt_local1185570365_0001_m_000004_0 is done. And is in the process of committing 14/10/07 03:36:03 INFO mapred.LocalJobRunner: map 14/10/07 03:36:03 INFO mapred.Task: Task ‘attempt_local1185570365_0001_m_000004_0‘ done. 14/10/07 03:36:03 INFO mapred.LocalJobRunner: Finishing task: attempt_local1185570365_0001_m_000004_0 14/10/07 03:36:03 INFO mapred.LocalJobRunner: Starting task: attempt_local1185570365_0001_m_000005_0 14/10/07 03:36:03 INFO mapred.Task: Using ResourceCalculatorProcessTree : [ ] 14/10/07 03:36:03 INFO mapred.MapTask: Processing split: file:/opt/hadoop-2.5.1/input/httpfs-site.xml:0+620 14/10/07 03:36:03 INFO mapred.MapTask: Map output collector class = org.apache.hadoop.mapred.MapTask$MapOutputBuffer 14/10/07 03:36:03 INFO mapred.MapTask: (EQUATOR) 0 kvi 26214396(104857584) 14/10/07 03:36:03 INFO mapred.MapTask: mapreduce.task.io.sort.mb: 100 14/10/07 03:36:03 INFO mapred.MapTask: soft limit at 83886080 14/10/07 03:36:03 INFO mapred.MapTask: bufstart = 0; bufvoid = 104857600 14/10/07 03:36:03 INFO mapred.MapTask: kvstart = 26214396; length = 6553600 14/10/07 03:36:03 INFO mapred.LocalJobRunner: 14/10/07 03:36:03 INFO mapred.MapTask: Starting flush of map output 14/10/07 03:36:03 INFO mapred.Task: Task:attempt_local1185570365_0001_m_000005_0 is done. And is in the process of committing 14/10/07 03:36:03 INFO mapred.LocalJobRunner: map 14/10/07 03:36:03 INFO mapred.Task: Task ‘attempt_local1185570365_0001_m_000005_0‘ done. 14/10/07 03:36:03 INFO mapred.LocalJobRunner: Finishing task: attempt_local1185570365_0001_m_000005_0 14/10/07 03:36:03 INFO mapred.LocalJobRunner: map task executor complete. 14/10/07 03:36:03 INFO mapred.LocalJobRunner: Waiting for reduce tasks 14/10/07 03:36:03 INFO mapred.LocalJobRunner: Starting task: attempt_local1185570365_0001_r_000000_0 14/10/07 03:36:03 INFO mapred.Task: Using ResourceCalculatorProcessTree : [ ] 14/10/07 03:36:03 INFO mapred.ReduceTask: Using ShuffleConsumerPlugin: org.apache.hadoop.mapreduce.task.reduce.Shuffle@57931be2 14/10/07 03:36:03 INFO reduce.MergeManagerImpl: MergerManager: memoryLimit=363285696, maxSingleShuffleLimit=90821424, mergeThreshold=239768576, ioSortFactor=10, memToMemMergeOutputsThreshold=10 14/10/07 03:36:03 INFO reduce.EventFetcher: attempt_local1185570365_0001_r_000000_0 Thread started: EventFetcher for fetching Map Completion Events 14/10/07 03:36:03 INFO reduce.LocalFetcher: localfetcher#1 about to shuffle output of map attempt_local1185570365_0001_m_000001_0 decomp: 2 len: 6 to MEMORY 14/10/07 03:36:03 INFO reduce.InMemoryMapOutput: Read 2 bytes from map-output for attempt_local1185570365_0001_m_000001_0 14/10/07 03:36:03 INFO reduce.MergeManagerImpl: closeInMemoryFile -> map-output of size: 2, inMemoryMapOutputs.size() -> 1, commitMemory -> 0, usedMemory ->2 14/10/07 03:36:03 INFO mapreduce.Job: map 100% reduce 0% 14/10/07 03:36:03 INFO reduce.LocalFetcher: localfetcher#1 about to shuffle output of map attempt_local1185570365_0001_m_000004_0 decomp: 2 len: 6 to MEMORY 14/10/07 03:36:03 INFO reduce.InMemoryMapOutput: Read 2 bytes from map-output for attempt_local1185570365_0001_m_000004_0 14/10/07 03:36:03 INFO reduce.MergeManagerImpl: closeInMemoryFile -> map-output of size: 2, inMemoryMapOutputs.size() -> 2, commitMemory -> 2, usedMemory ->4 14/10/07 03:36:03 INFO reduce.LocalFetcher: localfetcher#1 about to shuffle output of map attempt_local1185570365_0001_m_000005_0 decomp: 2 len: 6 to MEMORY 14/10/07 03:36:03 INFO reduce.InMemoryMapOutput: Read 2 bytes from map-output for attempt_local1185570365_0001_m_000005_0 14/10/07 03:36:03 INFO reduce.MergeManagerImpl: closeInMemoryFile -> map-output of size: 2, inMemoryMapOutputs.size() -> 3, commitMemory -> 4, usedMemory ->6 14/10/07 03:36:03 INFO reduce.LocalFetcher: localfetcher#1 about to shuffle output of map attempt_local1185570365_0001_m_000002_0 decomp: 2 len: 6 to MEMORY 14/10/07 03:36:03 INFO reduce.InMemoryMapOutput: Read 2 bytes from map-output for attempt_local1185570365_0001_m_000002_0 14/10/07 03:36:03 INFO reduce.MergeManagerImpl: closeInMemoryFile -> map-output of size: 2, inMemoryMapOutputs.size() -> 4, commitMemory -> 6, usedMemory ->8 14/10/07 03:36:03 INFO reduce.LocalFetcher: localfetcher#1 about to shuffle output of map attempt_local1185570365_0001_m_000003_0 decomp: 2 len: 6 to MEMORY 14/10/07 03:36:03 INFO reduce.InMemoryMapOutput: Read 2 bytes from map-output for attempt_local1185570365_0001_m_000003_0 14/10/07 03:36:03 INFO reduce.MergeManagerImpl: closeInMemoryFile -> map-output of size: 2, inMemoryMapOutputs.size() -> 5, commitMemory -> 8, usedMemory ->10 14/10/07 03:36:03 INFO reduce.LocalFetcher: localfetcher#1 about to shuffle output of map attempt_local1185570365_0001_m_000000_0 decomp: 21 len: 25 to MEMORY 14/10/07 03:36:03 INFO reduce.InMemoryMapOutput: Read 21 bytes from map-output for attempt_local1185570365_0001_m_000000_0 14/10/07 03:36:03 INFO reduce.MergeManagerImpl: closeInMemoryFile -> map-output of size: 21, inMemoryMapOutputs.size() -> 6, commitMemory -> 10, usedMemory ->31 14/10/07 03:36:03 INFO reduce.EventFetcher: EventFetcher is interrupted.. Returning 14/10/07 03:36:03 INFO mapred.LocalJobRunner: 6 / 6 copied. 14/10/07 03:36:03 INFO reduce.MergeManagerImpl: finalMerge called with 6 in-memory map-outputs and 0 on-disk map-outputs 14/10/07 03:36:03 INFO mapred.Merger: Merging 6 sorted segments 14/10/07 03:36:03 INFO mapred.Merger: Down to the last merge-pass, with 1 segments left of total size: 10 bytes 14/10/07 03:36:03 INFO reduce.MergeManagerImpl: Merged 6 segments, 31 bytes to disk to satisfy reduce memory limit 14/10/07 03:36:03 INFO reduce.MergeManagerImpl: Merging 1 files, 25 bytes from disk 14/10/07 03:36:03 INFO reduce.MergeManagerImpl: Merging 0 segments, 0 bytes from memory into reduce 14/10/07 03:36:03 INFO mapred.Merger: Merging 1 sorted segments 14/10/07 03:36:03 INFO mapred.Merger: Down to the last merge-pass, with 1 segments left of total size: 10 bytes 14/10/07 03:36:03 INFO mapred.LocalJobRunner: 6 / 6 copied. 14/10/07 03:36:04 INFO Configuration.deprecation: mapred.skip.on is deprecated. Instead, use mapreduce.job.skiprecords 14/10/07 03:36:04 INFO mapred.Task: Task:attempt_local1185570365_0001_r_000000_0 is done. And is in the process of committing 14/10/07 03:36:04 INFO mapred.LocalJobRunner: 6 / 6 copied. 14/10/07 03:36:04 INFO mapred.Task: Task attempt_local1185570365_0001_r_000000_0 is allowed to commit now 14/10/07 03:36:04 INFO output.FileOutputCommitter: Saved output of task ‘attempt_local1185570365_0001_r_000000_0‘ to file:/opt/hadoop-2.5.1/grep-temp-767563685/_temporary/0/task_local1185570365_0001_r_000000 14/10/07 03:36:04 INFO mapred.LocalJobRunner: reduce > reduce 14/10/07 03:36:04 INFO mapred.Task: Task ‘attempt_local1185570365_0001_r_000000_0‘ done. 14/10/07 03:36:04 INFO mapred.LocalJobRunner: Finishing task: attempt_local1185570365_0001_r_000000_0 14/10/07 03:36:04 INFO mapred.LocalJobRunner: reduce task executor complete. 14/10/07 03:36:04 INFO mapreduce.Job: map 100% reduce 100% 14/10/07 03:36:04 INFO mapreduce.Job: Job job_local1185570365_0001 completed successfully 14/10/07 03:36:04 INFO mapreduce.Job: Counters: 33 File System Counters FILE: Number of bytes read=114663 FILE: Number of bytes written=1613316 FILE: Number of read operations=0 FILE: Number of large read operations=0 FILE: Number of write operations=0 Map-Reduce Framework Map input records=405 Map output records=1 Map output bytes=17 Map output materialized bytes=55 Input split bytes=657 Combine input records=1 Combine output records=1 Reduce input groups=1 Reduce shuffle bytes=55 Reduce input records=1 Reduce output records=1 Spilled Records=2 Shuffled Maps =6 Failed Shuffles=0 Merged Map outputs=6 GC time elapsed (ms)=225 CPU time spent (ms)=0 Physical memory (bytes) snapshot=0 Virtual memory (bytes) snapshot=0 Total committed heap usage (bytes)=1106100224 Shuffle Errors BAD_ID=0 CONNECTION=0 IO_ERROR=0 WRONG_LENGTH=0 WRONG_MAP=0 WRONG_REDUCE=0 File Input Format Counters Bytes Read=15649 File Output Format Counters Bytes Written=123 14/10/07 03:36:04 INFO jvm.JvmMetrics: Cannot initialize JVM Metrics with processName=JobTracker, sessionId= - already initialized org.apache.hadoop.mapred.FileAlreadyExistsException: Output directory file:/opt/hadoop-2.5.1/output already exists at org.apache.hadoop.mapreduce.lib.output.FileOutputFormat.checkOutputSpecs(FileOutputFormat.java:146) at org.apache.hadoop.mapreduce.JobSubmitter.checkSpecs(JobSubmitter.java:458) at org.apache.hadoop.mapreduce.JobSubmitter.submitJobInternal(JobSubmitter.java:343) at org.apache.hadoop.mapreduce.Job$10.run(Job.java:1285) at org.apache.hadoop.mapreduce.Job$10.run(Job.java:1282) at java.security.AccessController.doPrivileged(Native Method) at javax.security.auth.Subject.doAs(Subject.java:415) at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1614) at org.apache.hadoop.mapreduce.Job.submit(Job.java:1282) at org.apache.hadoop.mapreduce.Job.waitForCompletion(Job.java:1303) at org.apache.hadoop.examples.Grep.run(Grep.java:92) at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:70) at org.apache.hadoop.examples.Grep.main(Grep.java:101) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at org.apache.hadoop.util.ProgramDriver$ProgramDescription.invoke(ProgramDriver.java:72) at org.apache.hadoop.util.ProgramDriver.run(ProgramDriver.java:145) at org.apache.hadoop.examples.ExampleDriver.main(ExampleDriver.java:74) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at org.apache.hadoop.util.RunJar.main(RunJar.java:212)
原文地址：http://blog.csdn.net/testcs_dn/article/details/39853517
