前记：我们也搭建了hdfs，打算把其中的维护经历记录下来，以方便自己查找历史。
1：报错无法启动namenode
2016-11-21 10:34:46,072 INFO org.apache.hadoop.hdfs.server.namenode.FSImageFormatPBINode: Loading 177159 INodes.
2016-11-21 10:34:47,252 INFO org.apache.hadoop.hdfs.server.namenode.FSImageFormatProtobuf: Loaded FSImage in 1 seconds.
2016-11-21 10:34:47,253 INFO org.apache.hadoop.hdfs.server.namenode.FSImage: Loaded image for txid 454073842 from /data/hadoop/hadoop/tmp/dfs/name/current/fsimage_0000000000454073842
2016-11-21 10:34:47,258 INFO org.apache.hadoop.hdfs.server.namenode.FSImage: Reading org.apache.hadoop.hdfs.server.namenode.RedundantEditLogInputStream@32c8e539 expecting start txid #454073843
2016-11-21 10:34:47,260 INFO org.apache.hadoop.hdfs.server.namenode.FSImage: Start loading edits file http://hadoop3.i.zhihuishu.com:8480/getJournal?jid=zhscluster&segmentTxId=454073896&storageInfo=-63%3A1565372169%3A0%3ACID-6393e2a5-76a8-42dd-9c37-95d951ef6f30, http://hadoop1.i.zhihuishu.com:8480/getJournal?jid=zhscluster&segmentTxId=454073896&storageInfo=-63%3A1565372169%3A0%3ACID-6393e2a5-76a8-42dd-9c37-95d951ef6f30
2016-11-21 10:34:47,262 INFO org.apache.hadoop.hdfs.server.namenode.EditLogInputStream: Fast-forwarding stream ‘http://hadoop3.i.zhihuishu.com:8480/getJournal?jid=zhscluster&segmentTxId=454073896&storageInfo=-63%3A1565372169%3A0%3ACID-6393e2a5-76a8-42dd-9c37-95d951ef6f30, http://hadoop1.i.zhihuishu.com:8480/getJournal?jid=zhscluster&segmentTxId=454073896&storageInfo=-63%3A1565372169%3A0%3ACID-6393e2a5-76a8-42dd-9c37-95d951ef6f30′ to transaction ID 454073843
2016-11-21 10:34:47,263 INFO org.apache.hadoop.hdfs.server.namenode.EditLogInputStream: Fast-forwarding stream ‘http://hadoop3.i.zhihuishu.com:8480/getJournal?jid=zhscluster&segmentTxId=454073896&storageInfo=-63%3A1565372169%3A0%3ACID-6393e2a5-76a8-42dd-9c37-95d951ef6f30′ to transaction ID 454073843
2016-11-21 10:34:47,956 WARN org.apache.hadoop.hdfs.server.namenode.FSNamesystem: Encountered exception loading fsimage
java.io.IOException: There appears to be a gap in the edit log. We expected txid 454073843, but got txid 454073896.
at org.apache.hadoop.hdfs.server.namenode.MetaRecoveryContext.editLogLoaderPrompt(MetaRecoveryContext.java:94)
at org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.loadEditRecords(FSEditLogLoader.java:215)
at org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.loadFSEdits(FSEditLogLoader.java:143)
at org.apache.hadoop.hdfs.server.namenode.FSImage.loadEdits(FSImage.java:837)
at org.apache.hadoop.hdfs.server.namenode.FSImage.loadFSImage(FSImage.java:692)
at org.apache.hadoop.hdfs.server.namenode.FSImage.recoverTransitionRead(FSImage.java:294)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.loadFSImage(FSNamesystem.java:975)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.loadFromDisk(FSNamesystem.java:681)
at org.apache.hadoop.hdfs.server.namenode.NameNode.loadNamesystem(NameNode.java:584)
at org.apache.hadoop.hdfs.server.namenode.NameNode.initialize(NameNode.java:644)
at org.apache.hadoop.hdfs.server.namenode.NameNode.<init>(NameNode.java:811)
at org.apache.hadoop.hdfs.server.namenode.NameNode.<init>(NameNode.java:795)
at org.apache.hadoop.hdfs.server.namenode.NameNode.createNameNode(NameNode.java:1488)
at org.apache.hadoop.hdfs.server.namenode.NameNode.main(NameNode.java:1554)
2016-11-21 10:34:47,960 INFO org.mortbay.log: Stopped HttpServer2$SelectChannelConnectorWithSafeStartup@hadoop1.i.zhihuishu.com:50070
2016-11-21 10:34:47,961 INFO org.apache.hadoop.metrics2.impl.MetricsSystemImpl: Stopping NameNode metrics system…
2016-11-21 10:34:47,962 INFO org.apache.hadoop.metrics2.impl.MetricsSystemImpl: NameNode metrics system stopped.
2016-11-21 10:34:47,962 INFO org.apache.hadoop.metrics2.impl.MetricsSystemImpl: NameNode metrics system shutdown complete.
2016-11-21 10:34:47,962 ERROR org.apache.hadoop.hdfs.server.namenode.NameNode: Failed to start namenode.
java.io.IOException: There appears to be a gap in the edit log. We expected txid 454073843, but got txid 454073896.
at org.apache.hadoop.hdfs.server.namenode.MetaRecoveryContext.editLogLoaderPrompt(MetaRecoveryContext.java:94)
at org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.loadEditRecords(FSEditLogLoader.java:215)
at org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.loadFSEdits(FSEditLogLoader.java:143)
at org.apache.hadoop.hdfs.server.namenode.FSImage.loadEdits(FSImage.java:837)
at org.apache.hadoop.hdfs.server.namenode.FSImage.loadFSImage(FSImage.java:692)
at org.apache.hadoop.hdfs.server.namenode.FSImage.recoverTransitionRead(FSImage.java:294)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.loadFSImage(FSNamesystem.java:975)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.loadFromDisk(FSNamesystem.java:681)
at org.apache.hadoop.hdfs.server.namenode.NameNode.loadNamesystem(NameNode.java:584)
at org.apache.hadoop.hdfs.server.namenode.NameNode.initialize(NameNode.java:644)
at org.apache.hadoop.hdfs.server.namenode.NameNode.<init>(NameNode.java:811)
at org.apache.hadoop.hdfs.server.namenode.NameNode.<init>(NameNode.java:795)
at org.apache.hadoop.hdfs.server.namenode.NameNode.createNameNode(NameNode.java:1488)
at org.apache.hadoop.hdfs.server.namenode.NameNode.main(NameNode.java:1554)
2016-11-21 10:34:47,964 INFO org.apache.hadoop.util.ExitUtil: Exiting with status 1
2016-11-21 10:34:47,971 INFO org.apache.hadoop.hdfs.server.namenode.NameNode: SHUTDOWN_MSG:
/************************************************************
SHUTDOWN_MSG: Shutting down NameNode at rizhi143/10.45.53.143
************************************************************/
处理办法：网上有解决办法，http://blog.csdn.net/amber_amber/article/details/46896719。但是我测试的时候不可以，所以全部格式化了。
参考url：https://my.oschina.net/HIJAY/blog/220816
1、删除hdfs/data中的所有文件
2、bin/stop-all.sh
3、bin/hadoop namenode -format
4、bin/start-all.sh