今天在安装hadoop后，启动了namenode，在执行hadoop fs -put /tmp/test.dat /test命令后，报了下面的一个错：
13/11/05 23:40:36 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable 13/11/05 23:40:37 WARN hdfs.DFSClient: DataStreamer Exception org.apache.hadoop.ipc.RemoteException(java.io.IOException): File /test/test.dat._COPYING_ could only be replicated to 0 nodes instead of minReplication (=1). There are 0 datanode(s) running and no node(s) are excluded in this operation. at org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.chooseTarget(BlockManager.java:1384) at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getAdditionalBlock(FSNamesystem.java:2478) at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.addBlock(NameNodeRpcServer.java:555) at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.addBlock(ClientNamenodeProtocolServerSideTranslatorPB.java:387) at org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java:59582) at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:585) at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:1026) at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2048) at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2044) at java.security.AccessController.doPrivileged(Native Method) at javax.security.auth.Subject.doAs(Subject.java:415) at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1491) at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2042) at org.apache.hadoop.ipc.Client.call(Client.java:1347) at org.apache.hadoop.ipc.Client.call(Client.java:1300) at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:206) at com.sun.proxy.$Proxy9.addBlock(Unknown Source) 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.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:186) at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:102) at com.sun.proxy.$Proxy9.addBlock(Unknown Source) at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolTranslatorPB.addBlock(ClientNamenodeProtocolTranslatorPB.java:330) at org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.locateFollowingBlock(DFSOutputStream.java:1226) at org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.nextBlockOutputStream(DFSOutputStream.java:1078) at org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.run(DFSOutputStream.java:514) put: File /test/test.dat._COPYING_ could only be replicated to 0 nodes instead of minReplication (=1). There are 0 datanode(s) running and no node(s) are excluded in this operation. 13/11/05 23:40:37 ERROR hdfs.DFSClient: Failed to close file /test/test.dat._COPYING_ org.apache.hadoop.ipc.RemoteException(java.io.IOException): File /test/test.dat._COPYING_ could only be replicated to 0 nodes instead of minReplication (=1). There are 0 datanode(s) running and no node(s) are excluded in this operation. at org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.chooseTarget(BlockManager.java:1384) at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getAdditionalBlock(FSNamesystem.java:2478) at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.addBlock(NameNodeRpcServer.java:555) at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.addBlock(ClientNamenodeProtocolServerSideTranslatorPB.java:387) at org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java:59582) at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:585) at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:1026) at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2048) at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2044) at java.security.AccessController.doPrivileged(Native Method) at javax.security.auth.Subject.doAs(Subject.java:415) at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1491) at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2042) at org.apache.hadoop.ipc.Client.call(Client.java:1347) at org.apache.hadoop.ipc.Client.call(Client.java:1300) at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:206) at com.sun.proxy.$Proxy9.addBlock(Unknown Source) 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.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:186) at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:102) at com.sun.proxy.$Proxy9.addBlock(Unknown Source) at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolTranslatorPB.addBlock(ClientNamenodeProtocolTranslatorPB.java:330) at org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.locateFollowingBlock(DFSOutputStream.java:1226) at org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.nextBlockOutputStream(DFSOutputStream.java:1078) at org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.run(DFSOutputStream.java:514)
上面的意思大概是说只有0个datanode,也就是说没有连接到namenode的datanode，但是我到DN节点上jps，datanode进程是存在的；我又用hadoop dfsadmin -report命令查看，发现确实是0个DN......
这是后只有查看DN的日志：
edSleep(maxRetries=10, sleepTime=1 SECONDS) 2013-11-06 16:42:04,222 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: master1/10.95.3.100:8020. Already tried 9 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1 SECONDS) 2013-11-06 16:42:04,223 WARN org.apache.hadoop.hdfs.server.datanode.DataNode: Problem connecting to server: master1/10.95.3.100:8020 2013-11-06 16:42:10,226 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: master1/10.95.3.100:8020. Already tried 0 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1 SECONDS) 2013-11-06 16:42:11,228 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: master1/10.95.3.100:8020. Already tried 1 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1 SECONDS) 2013-11-06 16:42:12,230 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: master1/10.95.3.100:8020. Already tried 2 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1 SECONDS) 2013-11-06 16:42:13,232 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: master1/10.95.3.100:8020. Already tried 3 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1 SECONDS) 2013-11-06 16:42:14,234 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: master1/10.95.3.100:8020. Already tried 4 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1 SECONDS) 2013-11-06 16:42:15,238 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: master1/10.95.3.100:8020. Already tried 5 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1 SECONDS) 2013-11-06 16:42:16,241 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: master1/10.95.3.100:8020. Already tried 6 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1 SECONDS) 2013-11-06 16:42:17,243 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: master1/10.95.3.100:8020. Already tried 7 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1 SECONDS) 2013-11-06 16:42:18,245 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: master1/10.95.3.100:8020. Already tried 8 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1 SECONDS)
发现确实是DN一直连不上NN, 怀疑是防火墙的问题，因此把所有节点上的防火墙都关闭了，
上述错误消失，hdfs正常。