Hadoop格式化HDFS报错java.net.UnknownHostException: localhost.localdomain: localhost.localdomain

异常描述

在对HDFS格式化，执行hadoop namenode -format命令时，出现未知的主机名的问题，异常信息如下所示：

 [shirdrn@localhost bin]$ hadoop namenode -format11/06/22 07:33:31 INFO namenode.NameNode: STARTUP_MSG: /************************************************************STARTUP_MSG: Starting NameNodeSTARTUP_MSG:   host = java.net.UnknownHostException: localhost.localdomain: localhost.localdomainSTARTUP_MSG:   args = [-format]STARTUP_MSG:   version = 0.20.0STARTUP_MSG:   build = https://svn.apache.org/repos/asf/hadoop/core/branches/branch-0.20 -r 763504; compiled by 'ndaley' on Thu Apr  9 05:18:40 UTC 2009************************************************************/Re-format filesystem in /tmp/hadoop/hadoop-shirdrn/dfs/name ? (Y or N) Y11/06/22 07:33:36 INFO namenode.FSNamesystem: fsOwner=shirdrn,shirdrn11/06/22 07:33:36 INFO namenode.FSNamesystem: supergroup=supergroup11/06/22 07:33:36 INFO namenode.FSNamesystem: isPermissionEnabled=true11/06/22 07:33:36 INFO metrics.MetricsUtil: Unable to obtain hostNamejava.net.UnknownHostException: localhost.localdomain: localhost.localdomain        at java.net.InetAddress.getLocalHost(InetAddress.java:1353)        at org.apache.hadoop.metrics.MetricsUtil.getHostName(MetricsUtil.java:91)        at org.apache.hadoop.metrics.MetricsUtil.createRecord(MetricsUtil.java:80)        at org.apache.hadoop.hdfs.server.namenode.FSDirectory.initialize(FSDirectory.java:73)        at org.apache.hadoop.hdfs.server.namenode.FSDirectory.<init>(FSDirectory.java:68)        at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.<init>(FSNamesystem.java:370)        at org.apache.hadoop.hdfs.server.namenode.NameNode.format(NameNode.java:853)        at org.apache.hadoop.hdfs.server.namenode.NameNode.createNameNode(NameNode.java:947)        at org.apache.hadoop.hdfs.server.namenode.NameNode.main(NameNode.java:964)11/06/22 07:33:36 INFO common.Storage: Image file of size 97 saved in 0 seconds.11/06/22 07:33:36 INFO common.Storage: Storage directory /tmp/hadoop/hadoop-shirdrn/dfs/name has been successfully formatted.11/06/22 07:33:36 INFO namenode.NameNode: SHUTDOWN_MSG: /************************************************************SHUTDOWN_MSG: Shutting down NameNode at java.net.UnknownHostException: localhost.localdomain: localhost.localdomain************************************************************/

我们通过执行hostname命令可以看到：

[shirdrn@localhost bin]# hostnamelocalhost.localdomain

也就是说，Hadoop在格式化HDFS的时候，通过hostname命令获取到的主机名是localhost.localdomain，然后在/etc/hosts文件中进行映射的时候，没有找到，看下我的/etc/hosts内容：

[root@localhost bin]# cat /etc/hosts# Do not remove the following line, or various programs# that require network functionality will fail.127.0.0.1               localhost       localhost192.168.1.103           localhost       localhost

也就说，通过localhost.localdomain根本无法映射到一个IP地址，所以报错了。

此时，我们查看一下/etc/sysconfig/network文件：

NETWORKING=yesNETWORKING_IPV6=yesHOSTNAME=localhost.localdomain

可见，执行hostname获取到这里配置的HOSTNAME的值。

解决方法

修改/etc/sysconfig/network中HOSTNAME的值为localhost，或者自己指定的主机名，保证localhost在/etc/hosts文件中映射为正确的IP地址，然后重新启动网络服务：

[root@localhost bin]# /etc/rc.d/init.d/network restartShutting down interface eth0:  [  OK  ]Shutting down loopback interface:  [  OK  ]Bringing up loopback interface:  [  OK  ]Bringing up interface eth0:  Determining IP information for eth0... done.[  OK  ]

这时，再执行格式化HDFS命令，以及启动HDFS集群就正常了。

格式化：

[shirdrn@localhost bin]$ hadoop namenode -format11/06/22 08:02:37 INFO namenode.NameNode: STARTUP_MSG: /************************************************************STARTUP_MSG: Starting NameNodeSTARTUP_MSG:   host = localhost/127.0.0.1STARTUP_MSG:   args = [-format]STARTUP_MSG:   version = 0.20.0STARTUP_MSG:   build = https://svn.apache.org/repos/asf/hadoop/core/branches/branch-0.20 -r 763504; compiled by 'ndaley' on Thu Apr  9 05:18:40 UTC 2009************************************************************/11/06/22 08:02:37 INFO namenode.FSNamesystem: fsOwner=shirdrn,shirdrn11/06/22 08:02:37 INFO namenode.FSNamesystem: supergroup=supergroup11/06/22 08:02:37 INFO namenode.FSNamesystem: isPermissionEnabled=true11/06/22 08:02:37 INFO common.Storage: Image file of size 97 saved in 0 seconds.11/06/22 08:02:37 INFO common.Storage: Storage directory /tmp/hadoop/hadoop-shirdrn/dfs/name has been successfully formatted.11/06/22 08:02:37 INFO namenode.NameNode: SHUTDOWN_MSG: /************************************************************SHUTDOWN_MSG: Shutting down NameNode at localhost/127.0.0.1************************************************************/

启动：

[shirdrn@localhost bin]$ start-all.sh starting namenode, logging to /home/shirdrn/eclipse/eclipse-3.5.2/hadoop/hadoop-0.20.0/logs/hadoop-shirdrn-namenode-localhost.outlocalhost: starting datanode, logging to /home/shirdrn/eclipse/eclipse-3.5.2/hadoop/hadoop-0.20.0/logs/hadoop-shirdrn-datanode-localhost.outlocalhost: starting secondarynamenode, logging to /home/shirdrn/eclipse/eclipse-3.5.2/hadoop/hadoop-0.20.0/logs/hadoop-shirdrn-secondarynamenode-localhost.outstarting jobtracker, logging to /home/shirdrn/eclipse/eclipse-3.5.2/hadoop/hadoop-0.20.0/logs/hadoop-shirdrn-jobtracker-localhost.outlocalhost: starting tasktracker, logging to /home/shirdrn/eclipse/eclipse-3.5.2/hadoop/hadoop-0.20.0/logs/hadoop-shirdrn-tasktracker-localhost.out

查看：

[shirdrn@localhost bin]$ jps8192 TaskTracker7905 DataNode7806 NameNode8065 JobTracker8002 SecondaryNameNode8234 Jps