把本地文件系统，复制到dfs文件系统时报错的错
[hadoop@localhost ~]$ hdfs dfs -copyFromLocal /home/hadoop/mk.txt /xg_test/ 03:59:35,556 WARN hdfs.DataStreamer: DataStreamer Exception org.apache.hadoop.ipc.RemoteException(java.io.IOException): File /xg_test/mk.txt._COPYING_ could only be written to 0 of the 1 minReplication nodes. There are 0 datanode(s) running and no node(s) are excluded in this operation. at org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.chooseTarget4NewBlock(BlockManager.java:2116) at org.apache.hadoop.hdfs.server.namenode.FSDirWriteFileOp.chooseTargetForNewBlock(FSDirWriteFileOp.java:287) at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getAdditionalBlock(FSNamesystem.java:2688) at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.addBlock(NameNodeRpcServer.java:875) at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.addBlock(ClientNamenodeProtocolServerSideTranslatorPB.java:559) at org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java) at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:523) at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:991) at org.apache.hadoop.ipc.Server$RpcCall.run(Server.java:869) at org.apache.hadoop.ipc.Server$RpcCall.run(Server.java:815) at java.security.AccessController.doPrivileged(Native Method) at javax.security.auth.Subject.doAs(Subject.java:422) at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1682) at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2675) at org.apache.hadoop.ipc.Client.getRpcResponse(Client.java:1491) at org.apache.hadoop.ipc.Client.call(Client.java:1437) at org.apache.hadoop.ipc.Client.call(Client.java:1347) at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:228) at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:116) at com.sun.proxy.$Proxy11.addBlock(Unknown Source) at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolTranslatorPB.addBlock(ClientNamenodeProtocolTranslatorPB.java:504) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:422) at org.apache.hadoop.io.retry.RetryInvocationHandler$Call.invokeMethod(RetryInvocationHandler.java:165) at org.apache.hadoop.io.retry.RetryInvocationHandler$Call.invoke(RetryInvocationHandler.java:157) at org.apache.hadoop.io.retry.RetryInvocationHandler$Call.invokeOnce(RetryInvocationHandler.java:95) at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:359) at com.sun.proxy.$Proxy12.addBlock(Unknown Source) at org.apache.hadoop.hdfs.DFSOutputStream.addBlock(DFSOutputStream.java:1078) at org.apache.hadoop.hdfs.DataStreamer.locateFollowingBlock(DataStreamer.java:1865) at org.apache.hadoop.hdfs.DataStreamer.nextBlockOutputStream(DataStreamer.java:1668) at org.apache.hadoop.hdfs.DataStreamer.run(DataStreamer.java:716) copyFromLocal: File /xg_test/mk.txt._COPYING_ could only be written to 0 of the 1 minReplication nodes. There are 0 datanode(s) running and no node(s) are excluded in this operation.
这边出现上述问题格式化多次hadoop，导致datanode不正确，决解的办法是：
1、在hadoop数据目录下（安装目录或者自己配置的目录，根据实际情况而定）……/data/dfs/data，把里面的current文件夹删除
2、然后从新执行一下 hadoop namenode -format
3、再使用start-dfs.sh和start-yarn.sh 重启一下hadoop，用jps命令看一下就可以看见datanode启动成功后就可以了