Hadoop启动DataNode没报错，也没成功

先查看报错

先输入这两个参数查看启动datanode的报错情况

export HADOOP_ROOT_LOGGER=DEBUG,console

hdfs datanode

下面是我启动datanode报错信息：

INFO http.HttpServer2: HttpServer.start() threw a non Bind IOException
java.net.BindException: Port in use: localhost:0
        at org.apache.hadoop.http.HttpServer2.constructBindException(HttpServer2.java:1014)
        at org.apache.hadoop.http.HttpServer2.bindForSinglePort(HttpServer2.java:1037)
        at org.apache.hadoop.http.HttpServer2.openListeners(HttpServer2.java:1094)
        at org.apache.hadoop.http.HttpServer2.start(HttpServer2.java:951)
        at org.apache.hadoop.hdfs.server.datanode.web.DatanodeHttpServer.<init>(DatanodeHttpServer.java:143)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.startInfoServer(DataNode.java:962)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.startDataNode(DataNode.java:1370)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.<init>(DataNode.java:495)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.makeInstance(DataNode.java:2695)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.instantiateDataNode(DataNode.java:2598)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.createDataNode(DataNode.java:2645)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.secureMain(DataNode.java:2789)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.main(DataNode.java:2813)
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.mortbay.jetty.nio.SelectChannelConnector.open(SelectChannelConnector.java:216)
        at org.apache.hadoop.http.HttpServer2.bindListener(HttpServer2.java:1002)
        at org.apache.hadoop.http.HttpServer2.bindForSinglePort(HttpServer2.java:1033)

里面主要一个是 "Cannot assign requested address"和"Port in use: localhost:0" ，localhost为0，意思就是你的hosts文件可能没有localhost的ip映射。我赶紧vim /etc/hosts查看了一下hosts文件，果然只有我自己配的几个集群的映射。加上下面的就可以了

127.0.0.1  localhost

如果还报java.lang.IllegalArgumentException: Does not contain a valid host:port authority ，那就是你的host名字不合法。