Hadoop環境CDH4.4
今天年後第一天上班（實習中），還過一個月，實習第一份實習合同就到期了~
Hadoop集羣的虛擬環境看上去太亂，所以就將3個節點（1master + 2Slaves）重啓，結果NodeManager啓動失敗。查看日誌，記錄錯誤如下：
2014-02-10 18:24:07,635 FATAL org.apache.hadoop.yarn.server.nodemanager.NodeManager: Error starting NodeManager
org.apache.hadoop.yarn.YarnException: Failed to Start org.apache.hadoop.yarn.server.nodemanager.NodeManager
at org.apache.hadoop.yarn.service.CompositeService.start(CompositeService.java:78)
at org.apache.hadoop.yarn.server.nodemanager.NodeManager.start(NodeManager.java:196)
at org.apache.hadoop.yarn.server.nodemanager.NodeManager.initAndStartNodeManager(NodeManager.java:329)
at org.apache.hadoop.yarn.server.nodemanager.NodeManager.main(NodeManager.java:351)
Caused by: org.apache.hadoop.yarn.YarnException: Failed to Start org.apache.hadoop.yarn.server.nodemanager.containermanager.ContainerManagerImpl
at org.apache.hadoop.yarn.service.CompositeService.start(CompositeService.java:78)
at org.apache.hadoop.yarn.server.nodemanager.containermanager.ContainerManagerImpl.start(ContainerManagerImpl.java:248)
at org.apache.hadoop.yarn.service.CompositeService.start(CompositeService.java:68)
... 3 more
Caused by: org.apache.hadoop.yarn.YarnException: Failed to check for existence of remoteLogDir [/var/log/hadoop-yarn/apps]
at org.apache.hadoop.yarn.server.nodemanager.containermanager.logaggregation.LogAggregationService.verifyAndCreateRemoteLogDir(LogAggregationService.java:179)
at org.apache.hadoop.yarn.server.nodemanager.containermanager.logaggregation.LogAggregationService.start(LogAggregationService.java:132)
at org.apache.hadoop.yarn.service.CompositeService.start(CompositeService.java:68)
... 5 more
2014-02-10 18:24:07,647 INFO org.apache.hadoop.ipc.Server: Stopping server on 52154
日誌顯示：無法啓動NodeManager，無法啓動ContainerManager（也就是沒有分配資源容器管理進程），也無法檢查遠程日誌目錄（在HDFS上），原因鎖定，無法與Master（具體來說是ResourceManager）通信，然後到master上查看防火牆是否關閉，Soga，果然防火牆是開着的，由於重啓導致防火牆開啓了，然後博主將Master上的防火牆關閉，並且chkconfig iptables off進行永久關閉（重啓後不會自動開啓），再去Slave節點上啓動NodeManager，搞定！