1. 執行./sbin/start-dfs.sh后查看進程發現namecode進程沒有啟動成功，
2.查看對於日志文件logs/hadoop-root-namenode-VM-0-16-centos.log，出現如下錯誤提示：
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. 解決方案：
修改vim /etc/hosts，將本機映射IP修改成內網IP（申請的騰訊雲主機有內網IP和外網IP）
另外的SecondaryNameNode，資源管理節點等其他slave節點也是同樣修改/etc/hosts的本機為當前節點內網IP,查看后也恢復
4. 重新 執行./sbin/start-dfs.sh后查看進程發現namecode進程：
