我已经创建了一个hadoop集群，其中有1个主节点和2个从节点。我在*-site.xml文件中以最低规格运行它。
core-site.xml文件

<configuration>
    <property>
        <name>fs.defaultFS</name>
        <value>hdfs://10.0.0.51:9000</value>
    </property>
</configuration>

hfds-site.xml文件

<configuration>
    <property>
        <name>dfs.datanode.name.dir</name>
        <value>~/DNfiles</value>
    </property>
</configuration>

mapred-site.xml文件

<configuration>
    <property>
        <name>mapreduce.framework.name</name>
        <value>yarn</value>
    </property>
</configuration>

yarn-site.xml文件

<configuration>

    <!-- Site specific YARN configuration properties -->

    <property>
        <name>yarn.nodemanager.aux-services</name>
        <value>mapreduce_shuffle</value>
    </property>
    <property>
        <name>yarn.resourcemanager.resource-tracker.address</name>
        <value>10.0.0.51:8025</value>
    </property>
    <property>
        <name>yarn.resourcemanager.scheduler.address</name>
        <value>10.0.0.51:8030</value>
    </property>
    <property>
        <name>yarn.resourcemanager.address</name>
        <value>10.0.0.51:8050</value>
    </property>
</configuration>

问题是我能够格式化namenode，将文件放入hfs，但当我运行一个简单的例子时，我得到以下错误。

Container launch failed for container_1455133326738_0002_02_000007 : java.lang.IllegalArgumentException: java.net.UnknownHostException: hadoop-slave-2 at org.apache.hadoop.security.SecurityUtil.buildTokenService(SecurityUtil.java:377)
    at org.apache.hadoop.security.SecurityUtil.setTokenService(SecurityUtil.java:356)
    at org.apache.hadoop.yarn.util.ConverterUtils.convertFromYarn(ConverterUtils.java:238)
at org.apache.hadoop.yarn.client.api.impl.ContainerManagementProtocolProxy$ContainerManagementProtocolProxyData.newProxy(ContainerManagementProtocolProxy.java:266)
 at org.apache.hadoop.yarn.client.api.impl.ContainerManagementProtocolProxy$ContainerManagementProtocolProxyData.<init>(ContainerManagementProtocolProxy.java:244)
    at org.apache.hadoop.yarn.client.api.impl.ContainerManagementProtocolProxy.getProxy(ContainerManagementProtocolProxy.java:129)
    at org.apache.hadoop.mapreduce.v2.app.launcher.ContainerLauncherImpl.getCMProxy(ContainerLauncherImpl.java:409)
    at org.apache.hadoop.mapreduce.v2.app.launcher.ContainerLauncherImpl$Container.launch(ContainerLauncherImpl.java:138)
    at org.apache.hadoop.mapreduce.v2.app.launcher.ContainerLauncherImpl$EventProcessor.run(ContainerLauncherImpl.java:375)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.net.UnknownHostException: hadoop-slave-2

虽然程序继续通过与其他从机一起工作来完成，即1个从机可以访问，但其他从机不能访问，尽管它们具有相同的配置。因为我能够格式化所有文件，所以我假设主节点中的/etc/hosts文件可以。这是它的片段。

ubuntu@hadoop-master-1:~/hadoop-2.7.1/bin$ cat /etc/hosts
127.0.0.1 localhost
10.0.0.51 hadoop-master-1
10.0.0.36 hadoop-slave
10.0.0.38 hadoop-slave-2
10.0.0.39 hadoop-slave-1
10.0.0.40 hadoop-slave-3
10.0.0.41 hadoop-slave-4

从属主机文件

ubuntu@hadoop-slave-1:~/hadoop-2.7.1/bin$ cat /etc/hosts
127.0.0.1 localhost
10.0.0.39 hadoop-slave-1
10.0.0.51 hadoop-master-1

有人知道问题出在哪里吗？任何帮助或可能的指点将不胜感激。