java.net.ConnectException: Call From localhost/127.0.0.1 to localhost:8020 failed on connection

执行《Hadoop权威指南》范例3-2时报错
执行命令

 export HADOOP_CLASSPATH=ch03-hdfs.jar
 hadoop FileSystemCat hdfs://localhost/user/liuzc/quangle.txt

错误信息

Exception in thread "main" java.net.ConnectException: Call From localhost/127.0.0.1 to localhost:8020 failed on connection exception: java.net.ConnectException: Connection refused; For more details see:  http://wiki.apache.org/hadoop/ConnectionRefused
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
    at org.apache.hadoop.net.NetUtils.wrapWithMessage(NetUtils.java:792)
    at org.apache.hadoop.net.NetUtils.wrapException(NetUtils.java:732)
    at org.apache.hadoop.ipc.Client.call(Client.java:1479)
    at org.apache.hadoop.ipc.Client.call(Client.java:1412)
    at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:229)
    at com.sun.proxy.$Proxy10.getBlockLocations(Unknown Source)
    at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolTranslatorPB.getBlockLocations(ClientNamenodeProtocolTranslatorPB.java:255)
    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:191)
    at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:102)
    at com.sun.proxy.$Proxy11.getBlockLocations(Unknown Source)
    at org.apache.hadoop.hdfs.DFSClient.callGetBlockLocations(DFSClient.java:1226)
    at org.apache.hadoop.hdfs.DFSClient.getLocatedBlocks(DFSClient.java:1213)
    at org.apache.hadoop.hdfs.DFSClient.getLocatedBlocks(DFSClient.java:1201)
    at org.apache.hadoop.hdfs.DFSInputStream.fetchLocatedBlocksAndGetLastBlockLength(DFSInputStream.java:306)
    at org.apache.hadoop.hdfs.DFSInputStream.openInfo(DFSInputStream.java:272)
    at org.apache.hadoop.hdfs.DFSInputStream.(DFSInputStream.java:264)
    at org.apache.hadoop.hdfs.DFSClient.open(DFSClient.java:1526)
    at org.apache.hadoop.hdfs.DistributedFileSystem$3.doCall(DistributedFileSystem.java:303)
    at org.apache.hadoop.hdfs.DistributedFileSystem$3.doCall(DistributedFileSystem.java:299)
    at org.apache.hadoop.fs.FileSystemLinkResolver.resolve(FileSystemLinkResolver.java:81)
    at org.apache.hadoop.hdfs.DistributedFileSystem.open(DistributedFileSystem.java:299)
    at org.apache.hadoop.fs.FileSystem.open(FileSystem.java:769)
    at FileSystemCat.main(FileSystemCat.java:19)
Caused by: java.net.ConnectException: Connection refused
    at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
    at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:717)
    at org.apache.hadoop.net.SocketIOWithTimeout.connect(SocketIOWithTimeout.java:206)
    at org.apache.hadoop.net.NetUtils.connect(NetUtils.java:531)
    at org.apache.hadoop.net.NetUtils.connect(NetUtils.java:495)
    at org.apache.hadoop.ipc.Client$Connection.setupConnection(Client.java:614)
    at org.apache.hadoop.ipc.Client$Connection.setupIOstreams(Client.java:712)
    at org.apache.hadoop.ipc.Client$Connection.access$2900(Client.java:375)
    at org.apache.hadoop.ipc.Client.getConnection(Client.java:1528)
    at org.apache.hadoop.ipc.Client.call(Client.java:1451)
    ... 24 more

解决方案
修改core-site.xml文件为

<configuration>

 <property>
   <name>fs.defaultFSname>
   <value>hdfs://hadoop01:8020value>
 property>

 <property>
   <name>hadoop.tmp.dirname>
   <value>/usr/local/hadoop-2.7.3/datavalue>
 property>
configuration>

fs.defaultFS属性的端口原来配置为9000

<property>
   <name>fs.defaultFSname>
   <value>hdfs://hadoop01:9000value>
 property>

改为8020重启hadoop就好了

<property>
   <name>fs.defaultFSname>
   <value>hdfs://hadoop01:8020value>
 property>