我有一个由两台机器组成的Hadoop 2.5集群，在从机上，数据节点出现UnregisteredNodeException故障。这是主配置：
master$ jps
5036 Jps
7145 DataNode
918 ResourceManager
7338 SecondaryNameNode
6986 NameNode
1105 NodeManager
对于从属
slave$ jps
15950 Jps
26650 NodeManager
以下是来自hadoop-hadoop-datanode-slave.log:的完整堆栈跟踪
2014-10-23 19:43:46,895 WARN org.apache.hadoop.hdfs.server.datanode.DataNode: Block pool BP-8947225-127.0.1.1-1409591980216 (Datanode Uuid 5c9f00ab-1d75-4706-8ed8-bfb449174c9a) service to hadoop-server/192.168.2.72:8020 is shutting down
org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.hdfs.protocol.UnregisteredNodeException): Data node DatanodeRegistration(192.168.2.73, datanodeUuid=5c9f00ab-1d75-4706-8ed8-bfb449174c9a, infoPort=50075, ipcPort=50020, storageInfo=lv=-55;cid=CID-ab378c59-62ed-44ff-8814-03b5b733b6fa;nsid=1290295317;c=0) is attempting to report storage ID 5c9f00ab-1d75-4706-8ed8-bfb449174c9a. Node 192.168.2.72:50010 is expected to serve this storage.
at org.apache.hadoop.hdfs.server.blockmanagement.DatanodeManager.getDatanode(DatanodeManager.java:475)
at org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.processReport(BlockManager.java:1702)
at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.blockReport(NameNodeRpcServer.java:1049)
at org.apache.hadoop.hdfs.protocolPB.DatanodeProtocolServerSideTranslatorPB.blockReport(DatanodeProtocolServerSideTranslatorPB.java:152)
at org.apache.hadoop.hdfs.protocol.proto.DatanodeProtocolProtos$DatanodeProtocolService$2.callBlockingMethod(DatanodeProtocolProtos.java:28061)
at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:585)
at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:928)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2013)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2009)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:415)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1614)
at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2007)
at org.apache.hadoop.ipc.Client.call(Client.java:1411)
at org.apache.hadoop.ipc.Client.call(Client.java:1364)
at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:206)
at com.sun.proxy.$Proxy11.blockReport(Unknown Source)
at sun.reflect.GeneratedMethodAccessor5.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:187)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:102)
at com.sun.proxy.$Proxy11.blockReport(Unknown Source)
at org.apache.hadoop.hdfs.protocolPB.DatanodeProtocolClientSideTranslatorPB.blockReport(DatanodeProtocolClientSideTranslatorPB.java:214)
at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.blockReport(BPServiceActor.java:476)
at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.offerService(BPServiceActor.java:699)
at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.run(BPServiceActor.java:834)
at java.lang.Thread.run(Thread.java:745)
当我在两台机器中的任何一台上发布hdfs dfsadmin -report时，我会看到以下内容：
14/10/31 10:48:34 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
Configured Capacity: 12547440640 (11.69 GB)
Present Capacity: 4710391808 (4.39 GB)
DFS Remaining: 4504489984 (4.20 GB)
DFS Used: 205901824 (196.36 MB)
DFS Used%: 4.37%
Under replicated blocks: 4
Blocks with corrupt replicas: 0
Missing blocks: 0
-------------------------------------------------
Live datanodes (1):
Name: 192.168.2.72:50010 (hadoop-server)
Hostname: hadoop-server
Decommission Status : Normal
Configured Capacity: 12547440640 (11.69 GB)
DFS Used: 205901824 (196.36 MB)
Non DFS Used: 7837048832 (7.30 GB)
DFS Remaining: 4504489984 (4.20 GB)
DFS Used%: 1.64%
DFS Remaining%: 35.90%
Configured Cache Capacity: 0 (0 B)
Cache Used: 0 (0 B)
Cache Remaining: 0 (0 B)
Cache Used%: 100.00%
Cache Remaining%: 0.00%
Xceivers: 1
Last contact: Fri Oct 31 10:48:35 CET 2014
此外，我可以从Resource Manger Web UI中查看/监视从属机器，那么是什么导致了此故障，以及如何修复它？
我实际上复制了一个vm来创建从机，这导致了所有节点都有相同UUID的情况。所以（正如这里所讨论的）我关闭了从属服务器中的服务：
hadoop-daemon.sh stop datanode
yarn-daemon.sh stop nodemanager
然后，我删除了datanode和namenode目录（分别位于dfs.datanode.data.dir和dfs.namenode.data.dir中）。然后，重新启动datanode和namenode。现在我可以看到数据节点启动并运行：
$ jps
17135 NodeManager
17290 DataNode
18221 Jps