我只有一台机器运行namenode和datanode。机器重新启动。现在由于不正确的关闭，namenode 没有出现。日志说namenode没有格式化。我怎么把它带回来？我有很多数据存储在其中，我不能丢失它。
2013-06-07 16:58:50,207 INFO org.apache.hadoop.hdfs.server.namenode.NameNode: STARTUP_MSG:
/************************************************************
STARTUP_MSG: Starting NameNode
STARTUP_MSG: host = Server/10.15.21.21
STARTUP_MSG: args = []
STARTUP_MSG: version = 0.20.2-cdh3u6
STARTUP_MSG: build = file:///data/1/tmp/nightly_2013-03-20_11-32-44_3/hadoop-0.20-0.20.2+923.479-1~lucid -r efb405d2aa54039bdf39e0733cd0bb9423a1eb0a; compiled by 'root' on Wed Mar 20 13:10:08 PDT 2013
************************************************************/
2013-06-07 16:58:50,559 INFO org.apache.hadoop.metrics.jvm.JvmMetrics: Initializing JVM Metrics with processName=NameNode, sessionId=null
2013-06-07 16:58:50,563 INFO org.apache.hadoop.hdfs.server.namenode.metrics.NameNodeMetrics: Initializing NameNodeMeterics using context object:org.apache.hadoop.metrics.spi.NullContext
2013-06-07 16:58:50,606 INFO org.apache.hadoop.hdfs.util.GSet: VM type = 64-bit
2013-06-07 16:58:50,606 INFO org.apache.hadoop.hdfs.util.GSet: 2% max memory = 17.77875 MB
2013-06-07 16:58:50,606 INFO org.apache.hadoop.hdfs.util.GSet: capacity = 2^21 = 2097152 entries
2013-06-07 16:58:50,606 INFO org.apache.hadoop.hdfs.util.GSet: recommended=2097152, actual=2097152
2013-06-07 16:58:50,671 INFO org.apache.hadoop.hdfs.server.namenode.FSNamesystem: fsOwner=hdfs (auth:SIMPLE)
2013-06-07 16:58:50,672 INFO org.apache.hadoop.hdfs.server.namenode.FSNamesystem: supergroup=supergroup
2013-06-07 16:58:50,672 INFO org.apache.hadoop.hdfs.server.namenode.FSNamesystem: isPermissionEnabled=true
2013-06-07 16:58:50,705 INFO org.apache.hadoop.hdfs.server.namenode.FSNamesystem: dfs.block.invalidate.limit=1000
2013-06-07 16:58:50,705 INFO org.apache.hadoop.hdfs.server.namenode.FSNamesystem: isAccessTokenEnabled=false accessKeyUpdateInterval=0 min(s), accessTokenLifetime=0 min(s)
2013-06-07 16:58:50,729 INFO org.apache.hadoop.hdfs.server.namenode.metrics.FSNamesystemMetrics: Initializing FSNamesystemMetrics using context object:org.apache.hadoop.metrics.spi.NullContext
2013-06-07 16:58:50,805 ERROR org.apache.hadoop.hdfs.server.namenode.FSNamesystem: FSNamesystem initialization failed.
java.io.IOException: NameNode is not formatted.
at org.apache.hadoop.hdfs.server.namenode.FSImage.recoverTransitionRead(FSImage.java:336)
at org.apache.hadoop.hdfs.server.namenode.FSDirectory.loadFSImage(FSDirectory.java:110)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.initialize(FSNamesystem.java:379)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.<init>(FSNamesystem.java:342)
at org.apache.hadoop.hdfs.server.namenode.NameNode.initialize(NameNode.java:307)
at org.apache.hadoop.hdfs.server.namenode.NameNode.<init>(NameNode.java:568)
at org.apache.hadoop.hdfs.server.namenode.NameNode.createNameNode(NameNode.java:1444)
at org.apache.hadoop.hdfs.server.namenode.NameNode.main(NameNode.java:1453)
2013-06-07 16:58:50,807 ERROR org.apache.hadoop.hdfs.server.namenode.NameNode: java.io.IOException: NameNode is not formatted.
at org.apache.hadoop.hdfs.server.namenode.FSImage.recoverTransitionRead(FSImage.java:336)
at org.apache.hadoop.hdfs.server.namenode.FSDirectory.loadFSImage(FSDirectory.java:110)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.initialize(FSNamesystem.java:379)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.<init>(FSNamesystem.java:342)
at org.apache.hadoop.hdfs.server.namenode.NameNode.initialize(NameNode.java:307)
at org.apache.hadoop.hdfs.server.namenode.NameNode.<init>(NameNode.java:568)
at org.apache.hadoop.hdfs.server.namenode.NameNode.createNameNode(NameNode.java:1444)
at org.apache.hadoop.hdfs.server.namenode.NameNode.main(NameNode.java:1453)
2013-06-07 16:58:50,808 INFO org.apache.hadoop.hdfs.server.namenode.NameNode: SHUTDOWN_MSG:
/************************************************************
SHUTDOWN_MSG: Shutting down NameNode at Server/10.15.21.21
************************************************************/