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hadoop集群部署上后，在服務器中運行hadoop自帶的jar包中的實例報錯
HADOOP_MAPRED_HOME=${full path of your hadoop distribution directory}
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異常一：
2018-01-09 03:25:37,250 INFO mapreduce.Job: Job job_1515468264727_0001 failed with state FAILED due to: Application application_1515468264727_0001 failed 2 times due to AM Container for appattempt_1515468264727_0001_000002 exited with exitCode: 1
Failing this attempt.Diagnostics: [2018-01-09 03:25:36.447]Exception from container-launch.
Container id: container_1515468264727_0001_02_000001
Exit code: 1
[2018-01-09 03:25:36.499]Container exited with a non-zero exit code 1. Error file: prelaunch.err.
Last 4096 bytes of prelaunch.err :
Last 4096 bytes of stderr :
Error: Could not find or load main class org.apache.hadoop.mapreduce.v2.app.MRAppMaster
Please check whether your etc/hadoop/mapred-site.xml contains the below configuration:
<property>
<name>yarn.app.mapreduce.am.env</name>
<value>HADOOP_MAPRED_HOME=${full path of your hadoop distribution directory}</value>
</property>
<property>
<name>mapreduce.map.env</name>
<value>HADOOP_MAPRED_HOME=${full path of your hadoop distribution directory}</value>
</property>
<property>
<name>mapreduce.reduce.env</name>
<value>HADOOP_MAPRED_HOME=${full path of your hadoop distribution directory}</value>
</property>
解決方法：按錯誤提示，在mapred-site.xml配置文件中添加hadoop根目錄
1.先運行hadoop classpath得到classpath
將得到的classpath全部復制到mapred-site.xml中，配置
<property>
<name>yarn.app.mapreduce.am.env</name>
<value>HADOOP_MAPRED_HOME=${full path of your hadoop distribution directory}（將這一串紅字用得到的classpath代替）</value>
</property>
<property>
<name>mapreduce.map.env</name>
<value>HADOOP_MAPRED_HOME=${full path of your hadoop distribution directory}（將這一串紅字用得到的classpath代替）</value>
</property>
<property>
<name>mapreduce.reduce.env</name>
<value>HADOOP_MAPRED_HOME=${full path of your hadoop distribution directory}（將這一串紅字用得到的classpath代替）</value>
</property>
配置結束關閉mapred-site.xml
重新啟動集群，再在share文件中運行
得到結果：
測試成功！！