hadoop2.7本机运行mapreduce显示拒绝连接

hadoop2.7伪分布模式

ubuntu14.04

今天在本机运行hadoop程序./bin/yarn jar ./share/hadoop/mapreduce/hadoop-mapreduce-examples-2.7.1.jar时，显示

java.io.IOException: java.net.ConnectException: Call From znb/127.0.0.1 to 0.0.0.0:10020 failed on connection exception: java.net.ConnectException: 拒绝连接; For more details see:  http://wiki.apache.org/hadoop/ConnectionRefused

java.io.IOException: java.net.ConnectException: Call From znb/127.0.0.1 to 0.0.0.0:10020 failed on connection exception: java.net.ConnectException: 拒绝连接; For more details see:  http://wiki.apache.org/hadoop/ConnectionRefused
	at org.apache.hadoop.mapred.ClientServiceDelegate.invoke(ClientServiceDelegate.java:343)
	at org.apache.hadoop.mapred.ClientServiceDelegate.getJobStatus(ClientServiceDelegate.java:428)
	at org.apache.hadoop.mapred.YARNRunner.getJobStatus(YARNRunner.java:568)
	at org.apache.hadoop.mapreduce.Job$1.run(Job.java:323)
	at org.apache.hadoop.mapreduce.Job$1.run(Job.java:320)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAs(Subject.java:415)
	at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1657)
	at org.apache.hadoop.mapreduce.Job.updateStatus(Job.java:320)
	at org.apache.hadoop.mapreduce.Job.isSuccessful(Job.java:616)
	at org.apache.hadoop.mapreduce.Job.waitForCompletion(Job.java:1323)
	at org.apache.hadoop.examples.QuasiMonteCarlo.estimatePi(QuasiMonteCarlo.java:306)
	at org.apache.hadoop.examples.QuasiMonteCarlo.run(QuasiMonteCarlo.java:354)
	at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:70)
	at org.apache.hadoop.examples.QuasiMonteCarlo.main(QuasiMonteCarlo.java:363)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:606)
	at org.apache.hadoop.util.ProgramDriver$ProgramDescription.invoke(ProgramDriver.java:71)
	at org.apache.hadoop.util.ProgramDriver.run(ProgramDriver.java:144)
	at org.apache.hadoop.examples.ExampleDriver.main(ExampleDriver.java:74)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:606)
	at org.apache.hadoop.util.RunJar.run(RunJar.java:221)
	at org.apache.hadoop.util.RunJar.main(RunJar.java:136)
Caused by: java.net.ConnectException: Call From znb/127.0.0.1 to 0.0.0.0:10020 failed on connection exception: java.net.ConnectException: 拒绝连接; For more details see:  http://wiki.apache.org/hadoop/ConnectionRefused
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
	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:1480)
	at org.apache.hadoop.ipc.Client.call(Client.java:1407)
	at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:229)
	at com.sun.proxy.$Proxy14.getJobReport(Unknown Source)
	at org.apache.hadoop.mapreduce.v2.api.impl.pb.client.MRClientProtocolPBClientImpl.getJobReport(MRClientProtocolPBClientImpl.java:133)
	at sun.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:606)
	at org.apache.hadoop.mapred.ClientServiceDelegate.invoke(ClientServiceDelegate.java:324)
	... 27 more
Caused by: java.net.ConnectException: 拒绝连接
	at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
	at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:739)
	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$Connection.setupConnection(Client.java:609)
	at org.apache.hadoop.ipc.Client$Connection.setupIOstreams(Client.java:707)
	at org.apache.hadoop.ipc.Client$Connection.access$2800(Client.java:370)
	at org.apache.hadoop.ipc.Client.getConnection(Client.java:1529)
	at org.apache.hadoop.ipc.Client.call(Client.java:1446)
	... 35 more

虽然正常启动了Hadoop2.7，但是运行实例还是报错。

解决办法：运行 telnet 127.0.0.1或者telnet localhost即可。