dataNode 有守护进行，但hdfs web页面上显示没有live node。
错误日志：
2017-06-21 17:44:59,513 ERROR org.apache.hadoop.hdfs.server.datanode.DataNode: Initialization failed for Block pool BP-1394689615-10.85.123.43-1498038283287 (Datanode Uuid null) service to /10.85.123.43:9000 Datanode denied communication with namenode because hostname cannot be resolved (ip=10.85.123.44, hostname=10.85.123.44): DatanodeRegistration(0.0.0.0:50010, datanodeUuid=e086ba2d-fe65-4ba7-a6c2-a4829ac9e708, infoPort=50075, infoSecurePort=0, ipcPort=50020, storageInfo=lv=-56;cid=CID-9bfeb191-6823-4f9e-9daa-e31c797e70df;nsid=523094968;c=0)
at org.apache.hadoop.hdfs.server.blockmanagement.DatanodeManager.registerDatanode(DatanodeManager.java:873)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.registerDatanode(FSNamesystem.java:4529)
at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.registerDatanode(NameNodeRpcServer.java:1286)
at org.apache.hadoop.hdfs.protocolPB.DatanodeProtocolServerSideTranslatorPB.registerDatanode(DatanodeProtocolServerSideTranslatorPB.java:96)
at org.apache.hadoop.hdfs.protocol.proto.DatanodeProtocolProtos$DatanodeProtocolService$2.callBlockingMethod(DatanodeProtocolProtos.java:28752)
at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:616)
at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:982)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2049)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2045)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:422)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1698)
at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2043)
由于配置hadoop没有使用host+hostName的配置方式，导致了hadoop无法解析DataNode，对DataNode的注册失败。
解决方案：hdfs-site.xml中添加
<property> <name>dfs.namenode.datanode.registration.ip-hostname-check</name> <value>false</value> </property>