Hadoop部署在RedHat Linux 5上常見錯誤及解決方案
來源：互聯網
上載者：User
遇到的問題：
1、在hadoop conf下執行命令： hadoop-daemon.sh start datanode，無法啟動hadoop datanode：
[hadoop@master conf]$ hadoop-daemon.sh start datanode
Warning: $HADOOP_HOME is deprecated.
starting datanode, logging to /opt/modules/hadoop/hadoop-1.1.2/libexec/.. /logs/hadoop-hadoop-datanode-master.out
[hadoop@master conf]$ jps
4662 NameNode
4819 Jps
[hadoop@master conf]$ tail -300f /opt/modules/hadoop/hadoop-1.1.2/libexec/.. /logs/hadoop-hadoop-datanode-master.log
報錯：
Incompatible HTTP://www.aliyun.com/zixun/aggregation/11696.html">namespaceIDs in /data/hadoop/hdfs/data: namenode namespaceID = 573007068; datanode namespaceID = 1802250800
解決方法：用網上介紹的第一種：刪除data目錄（即是在hdfs-site.xml檔中配置的dfs.data.dir目錄）然後重啟datanode。
[hadoop@master conf]$ rm -rf /data/hadoop/hdfs/data
[hadoop@master conf]$ ll /data/hadoop/hdfs/
total 8
drwxrwxr-x 5 hadoop hadoop 4096 Jul 6 08:17 name
drwxrwxr-x 2 hadoop hadoop 4096 Jul 2 06:59 namesecondary
[hadoop@master conf]$ hadoop-daemon.sh start datanode
2、啟動Jobtracker時報錯：
2013-07-06 10:03:09,584 INFO org.apache.hadoop.mapred.JobTracker: problem cleaning system directory: hdfs://master :9000/data/hadoop/mapred/mrsystem
org.apache.hadoop.ipc.RemoteException: java.io.FileNotFoundException: Parent path is not a directory: /data
原因是：有個/data檔（注意不是資料夾，跟參數剛好不相匹配），也可以通過網頁中看：
NameNode 'master:9000'
Started: Sat Jul 06 09:54:05 PDT 2013
Version: 1.1.2, r1440782
Compiled: Thu Jan 31 02:03:24 UTC 2013 by hortonfo
Upgrades: There are no upgrades in progress.
Browse the filesystem
Namenode Logs
解決方法：刪除掉改檔：hadoop fs -rmr /data 即ok
3、在hadoop中編譯eclipse匯出的jar包時報錯：
[hadoop@master hadoop-1.1.2]$ hadoop jar hdfs1.jar com.hadoop.hdfs.HDFSMkdir
Warning: $HADOOP_HOME is deprecated.
Exception in thread "main" java.lang.UnsupportedClassVersionError: com/hadoop/hdfs/HDFSMkdir : Unsupported major.m inor version 51.0
原因：eclipse中所用java版本與hadoop所用java版本不一致。
解決方法：更改eclipse中的java版本重新匯出jar包。
