我已经用namenode 192.168.56.101 secondarynode 192.168.56.102 datanode1 192.168.56.103配置了hadoop集群
运行start-dfs.sh和start-mapred.sh之后
除了datanode1，所有的恶魔都起来了，我不知道为什么！
这是datanode1的日志

2015-03-17 09:35:58,224 INFO org.apache.hadoop.hdfs.server.datanode.DataNode: STARTUP_MSG: 
/************************************************************
STARTUP_MSG: Starting DataNode
STARTUP_MSG:   host = datanode1/192.168.56.103
STARTUP_MSG:   args = []
STARTUP_MSG:   version = 1.2.0
STARTUP_MSG:   build = https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1.2 -r 1479473; compiled by 'hortonfo' on Mon May  6 06:59:37 UTC 2013
STARTUP_MSG:   java = 1.7.0_75

************************************************************/

2015-03-17 09:35:58,572 INFO org.apache.hadoop.metrics2.impl.MetricsConfig: loaded properties from hadoop-metrics2.properties
2015-03-17 09:35:58,596 INFO org.apache.hadoop.metrics2.impl.MetricsSourceAdapter: MBean for source MetricsSystem,sub=Stats registered.
2015-03-17 09:35:58,600 INFO org.apache.hadoop.metrics2.impl.MetricsSystemImpl: Scheduled snapshot period at 10 second(s).
2015-03-17 09:35:58,600 INFO org.apache.hadoop.metrics2.impl.MetricsSystemImpl: DataNode metrics system started
2015-03-17 09:35:58,901 INFO org.apache.hadoop.metrics2.impl.MetricsSourceAdapter: MBean for source ugi registered.
2015-03-17 09:35:58,921 WARN org.apache.hadoop.metrics2.impl.MetricsSystemImpl: Source name ugi already exists!
2015-03-17 09:36:04,816 ERROR org.apache.hadoop.hdfs.server.datanode.DataNode: java.io.IOException: Incompatible namespaceIDs in /usr/local/hadoop/tmp/dfs/data: namenode namespaceID = 941733068; datanode namespaceID = 1890117295
    at org.apache.hadoop.hdfs.server.datanode.DataStorage.doTransition(DataStorage.java:232)
    at org.apache.hadoop.hdfs.server.datanode.DataStorage.recoverTransitionRead(DataStorage.java:147)
    at org.apache.hadoop.hdfs.server.datanode.DataNode.startDataNode(DataNode.java:412)
    at org.apache.hadoop.hdfs.server.datanode.DataNode.<init>(DataNode.java:319)
    at org.apache.hadoop.hdfs.server.datanode.DataNode.makeInstance(DataNode.java:1698)
    at org.apache.hadoop.hdfs.server.datanode.DataNode.instantiateDataNode(DataNode.java:1637)
    at org.apache.hadoop.hdfs.server.datanode.DataNode.createDataNode(DataNode.java:1655)
    at org.apache.hadoop.hdfs.server.datanode.DataNode.secureMain(DataNode.java:1781)
    at org.apache.hadoop.hdfs.server.datanode.DataNode.main(DataNode.java:1798)

2015-03-17 09:36:04,820 INFO org.apache.hadoop.hdfs.server.datanode.DataNode: SHUTDOWN_MSG: 
/************************************************************
SHUTDOWN_MSG: Shutting down DataNode at datanode1/192.168.56.103

************************************************************/