在启动分布式文件系统时，出现以下异常。我正在使用hadoop2.6.0。

2015-08-26 23:10:58,222 FATAL datanode.DataNode (DataNode.java:secureMain(2385)) - Exception in secureMain
    java.net.UnknownHostException: IM1948-X0: IM1948-X0
            at java.net.InetAddress.getLocalHost(InetAddress.java:1475)
            at org.apache.hadoop.security.SecurityUtil.getLocalHostName(SecurityUtil.java:187)
            at org.apache.hadoop.security.SecurityUtil.login(SecurityUtil.java:207)
            at org.apache.hadoop.hdfs.server.datanode.DataNode.instantiateDataNode(DataNode.java:2153)
            at org.apache.hadoop.hdfs.server.datanode.DataNode.createDataNode(DataNode.java:2202)
            at org.apache.hadoop.hdfs.server.datanode.DataNode.secureMain(DataNode.java:2378)
            at org.apache.hadoop.hdfs.server.datanode.DataNode.main(DataNode.java:2402)
    Caused by: java.net.UnknownHostException: IM1948-X0
            at java.net.Inet4AddressImpl.lookupAllHostAddr(Native Method)
            at java.net.InetAddress$1.lookupAllHostAddr(InetAddress.java:901)
            at java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1295)
            at java.net.InetAddress.getLocalHost(InetAddress.java:1471)
2015-08-26 23:10:58,227 INFO  util.ExitUtil (ExitUtil.java:terminate(124)) - Exiting with status 1
2015-08-26 23:10:58,229 INFO  datanode.DataNode (StringUtils.java:run(659)) - SHUTDOWN_MSG:
/************************************************************
SHUTDOWN_MSG: Shutting down DataNode at java.net.UnknownHostException: IM1948-X0: IM1948-X0

即使删除hadoop/hdfs data/current目录也无济于事；我尝试格式化namenode，但没有成功。这通常发生在我重新启动hadoop时。
总而言之，对于hadoop集群，datanode进程根本没有运行。