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：
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 [shirdrn@localhost bin]$ hadoop namenode -format  
11/06/22 07:33:31 INFO namenode.NameNode: STARTUP_MSG:   
/************************************************************  
STARTUP_MSG: Starting NameNode  
STARTUP_MSG:   host = java.net.UnknownHostException: localhost.localdomain: localhost.localdomain  
STARTUP_MSG:   args = [-format]  
STARTUP_MSG:   version = 0.20.0  
STARTUP_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) Y  
11/06/22 07:33:36 INFO namenode.FSNamesystem: fsOwner=shirdrn,shirdrn  
11/06/22 07:33:36 INFO namenode.FSNamesystem: supergroup=supergroup  
11/06/22 07:33:36 INFO namenode.FSNamesystem: isPermissionEnabled=true  
11/06/22 07:33:36 INFO metrics.MetricsUtil: Unable to obtain hostName  
java.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：
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[shirdrn@localhost bin]# hostname  
localhost.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：
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[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       localhost  
192.168.1.103           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：
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NETWORKING=yes  
NETWORKING_IPV6=yes  
HOSTNAME=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：
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[root@localhost bin]# /etc/rc.d/init.d/network restart  
Shutting 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：
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[shirdrn@localhost bin]$ hadoop namenode -format  
11/06/22 08:02:37 INFO namenode.NameNode: STARTUP_MSG:   
/************************************************************  
STARTUP_MSG: Starting NameNode  
STARTUP_MSG:   host = localhost/127.0.0.1  
STARTUP_MSG:   args = [-format]  
STARTUP_MSG:   version = 0.20.0  
STARTUP_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,shirdrn  
11/06/22 08:02:37 INFO namenode.FSNamesystem: supergroup=supergroup  
11/06/22 08:02:37 INFO namenode.FSNamesystem: isPermissionEnabled=true  
11/06/22 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：
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[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.out  
localhost: starting datanode, logging to /home/shirdrn/eclipse/eclipse-3.5.2/hadoop/hadoop-0.20.0/logs/hadoop-shirdrn-datanode-localhost.out  
localhost: starting secondarynamenode, logging to /home/shirdrn/eclipse/eclipse-3.5.2/hadoop/hadoop-0.20.0/logs/hadoop-shirdrn-secondarynamenode-localhost.out  
starting jobtracker, logging to /home/shirdrn/eclipse/eclipse-3.5.2/hadoop/hadoop-0.20.0/logs/hadoop-shirdrn-jobtracker-localhost.out  
localhost: starting tasktracker, logging to /home/shirdrn/eclipse/eclipse-3.5.2/hadoop/hadoop-0.20.0/logs/hadoop-shirdrn-tasktracker-localhost.out  
查看：
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[shirdrn@localhost bin]$ jps  
8192 TaskTracker  
7905 DataNode  
7806 NameNode  
8065 JobTracker  
8002 SecondaryNameNode  
8234 Jps