常见问题:

1.ResourceManager不能为0.0.0.0，见wiki，如果有这种情况可以设置yarn-site.xml

<property>  
    <name>yarn.resourcemanager.address</name>  
    <value>master:8032</value>  
  </property>  
  <property>  
    <name>yarn.resourcemanager.scheduler.address</name>  
    <value>master:8030</value>  
  </property>  
  <property>  
    <name>yarn.resourcemanager.resource-tracker.address</name>  
    <value>master:8031</value>  
  </property> 

2.设置mapreduce的内存，在mapred-site.xml

<property>
    <name>mapred.child.java.opts</name>
     <value>-Xmx512m</value>

</property>

3.重复尝试连接，16/07/01 10:11:34 INFO ipc.Client: Retrying connect to server: localhost/127.0.0.1:8032. Already tried 6 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)

检查jps，查看是否yarn没有启动

4.异常中断后，org.apache.Hadoop.dfs.SafeModeException: Cannot delete /user/hadoop/input. Name node is in safe mode ，处于安全模式

bin/hadoop dfsadmin -safemode leave

bin/hadoop dfsadmin -safemode enter 打开安全模式

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