1. 执行./sbin/start-dfs.sh后查看进程发现namecode进程没有启动成功，
2.查看对于日志文件logs/hadoop-root-namenode-VM-0-16-centos.log，出现如下错误提示：
2020-07-25 09:57:51,331 INFO org.apache.hadoop.http.HttpServer2: HttpServer.start() threw a non Bind IOException
java.net.BindException: Port in use: master:50070
at org.apache.hadoop.http.HttpServer2.constructBindException(HttpServer2.java:1198)
at org.apache.hadoop.http.HttpServer2.bindForSinglePort(HttpServer2.java:1220)
at org.apache.hadoop.http.HttpServer2.openListeners(HttpServer2.java:1279)
at org.apache.hadoop.http.HttpServer2.start(HttpServer2.java:1134)
at org.apache.hadoop.hdfs.server.namenode.NameNodeHttpServer.start(NameNodeHttpServer.java:177)
at org.apache.hadoop.hdfs.server.namenode.NameNode.startHttpServer(NameNode.java:869)
at org.apache.hadoop.hdfs.server.namenode.NameNode.initialize(NameNode.java:691)
at org.apache.hadoop.hdfs.server.namenode.NameNode.<init>(NameNode.java:937)
at org.apache.hadoop.hdfs.server.namenode.NameNode.<init>(NameNode.java:910)
at org.apache.hadoop.hdfs.server.namenode.NameNode.createNameNode(NameNode.java:1643)
at org.apache.hadoop.hdfs.server.namenode.NameNode.main(NameNode.java:1710)
Caused by: java.net.BindException: Cannot assign requested address
at sun.nio.ch.Net.bind0(Native Method)
at sun.nio.ch.Net.bind(Net.java:433)
at sun.nio.ch.Net.bind(Net.java:425)
at sun.nio.ch.ServerSocketChannelImpl.bind(ServerSocketChannelImpl.java:223)
at sun.nio.ch.ServerSocketAdaptor.bind(ServerSocketAdaptor.java:74)
at org.eclipse.jetty.server.ServerConnector.openAcceptChannel(ServerConnector.java:351)
at org.eclipse.jetty.server.ServerConnector.open(ServerConnector.java:319)
at org.apache.hadoop.http.HttpServer2.bindListener(HttpServer2.java:1185)
at org.apache.hadoop.http.HttpServer2.bindForSinglePort(HttpServer2.java:1216)
... 9 more
2020-07-25 09:57:51,336 INFO org.apache.hadoop.metrics2.impl.MetricsSystemImpl: Stopping NameNode metrics system...
2020-07-25 09:57:51,337 INFO org.apache.hadoop.metrics2.impl.MetricsSystemImpl: NameNode metrics system stopped.
2020-07-25 09:57:51,337 INFO org.apache.hadoop.metrics2.impl.MetricsSystemImpl: NameNode metrics system shutdown complete.
2020-07-25 09:57:51,337 ERROR org.apache.hadoop.hdfs.server.namenode.NameNode: Failed to start namenode.
java.net.BindException: Port in use: master:50070
at org.apache.hadoop.http.HttpServer2.constructBindException(HttpServer2.java:1198)
at org.apache.hadoop.http.HttpServer2.bindForSinglePort(HttpServer2.java:1220)
at org.apache.hadoop.http.HttpServer2.openListeners(HttpServer2.java:1279)
at org.apache.hadoop.http.HttpServer2.start(HttpServer2.java:1134)
at org.apache.hadoop.hdfs.server.namenode.NameNodeHttpServer.start(NameNodeHttpServer.java:177)
at org.apache.hadoop.hdfs.server.namenode.NameNode.startHttpServer(NameNode.java:869)
at org.apache.hadoop.hdfs.server.namenode.NameNode.initialize(NameNode.java:691)
at org.apache.hadoop.hdfs.server.namenode.NameNode.<init>(NameNode.java:937)
at org.apache.hadoop.hdfs.server.namenode.NameNode.<init>(NameNode.java:910)
at org.apache.hadoop.hdfs.server.namenode.NameNode.createNameNode(NameNode.java:1643)
at org.apache.hadoop.hdfs.server.namenode.NameNode.main(NameNode.java:1710)
Caused by: java.net.BindException: Cannot assign requested address
at sun.nio.ch.Net.bind0(Native Method)
at sun.nio.ch.Net.bind(Net.java:433)
at sun.nio.ch.Net.bind(Net.java:425)
at sun.nio.ch.ServerSocketChannelImpl.bind(ServerSocketChannelImpl.java:223)
at sun.nio.ch.ServerSocketAdaptor.bind(ServerSocketAdaptor.java:74)
at org.eclipse.jetty.server.ServerConnector.openAcceptChannel(ServerConnector.java:351)
at org.eclipse.jetty.server.ServerConnector.open(ServerConnector.java:319)
at org.apache.hadoop.http.HttpServer2.bindListener(HttpServer2.java:1185)
at org.apache.hadoop.http.HttpServer2.bindForSinglePort(HttpServer2.java:1216)
... 9 more
2020-07-25 09:57:51,338 INFO org.apache.hadoop.util.ExitUtil: Exiting with status 1: java.net.BindException: Port in use: master:50070
2020-07-25 09:57:51,375 INFO org.apache.hadoop.hdfs.server.namenode.NameNode: SHUTDOWN_MSG:
3. 解决方案：
修改vim /etc/hosts，将本机映射IP修改成内网IP（申请的腾讯云主机有内网IP和外网IP）
另外的SecondaryNameNode，资源管理节点等其他slave节点也是同样修改/etc/hosts的本机为当前节点内网IP,查看后也恢复
4. 重新 执行./sbin/start-dfs.sh后查看进程发现namecode进程：
