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解决办法：可能是修改 机器名导致的，修改hosts，写入hostname和IP，然后，try it agin！
解决办法：
当引入hadoop-common-2.2.0.jar包进行二次开发，比如读写HDFS文件时，初次运行报错。
java.io.IOException: No FileSystem for scheme: hdfs
at org.apache.hadoop.fs.FileSystem.getFileSystemClass(FileSystem.java:2421)
at org.apache.hadoop.fs.FileSystem.createFileSystem(FileSystem.java:2428)
at org.apache.hadoop.fs.FileSystem.access$200(FileSystem.java:88)
at org.apache.hadoop.fs.FileSystem$Cache.getInternal(FileSystem.java:2467)
at org.apache.hadoop.fs.FileSystem$Cache.get(FileSystem.java:2449)
at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:367)
at FileCopyToHdfs.readFromHdfs(FileCopyToHdfs.java:65)
at FileCopyToHdfs.main(FileCopyToHdfs.java:26)
这是因为该包下默认的core-default.xml没有配置如下属性：
fs.hdfs.impl
org.apache.hadoop.hdfs.DistributedFileSystem
The FileSystem for hdfs: uris.
< /property>
添加完后，问题解决。
建议下载hadoop-2.2.0源码，在源码修改core-default.xml文件后再编译打包，再在二次开发的工程引入新的jar包。
http://www.cnblogs.com/tangtianfly/p/3491133.html
http://www.cnblogs.com/tangtianfly/p/3491133.html
http://blog.csdn.net/u013281331/article/details/17992077
上属性指定fs.hdfs.impl的实现类。
解决办法：
时间不同步
su root
ntpdate 133.100.11.8
cd /usr/local/hbase/bin/
./hbase-daemon.sh start regionserver
解决办法：
打开hdfs-site.xml里配置的datanode和namenode对应的目录，分别打开current文件夹里的VERSION，可以看到clusterID项正如日志里记录的一样，确实不一致，修改datanode里VERSION文件的clusterID 与namenode里的一致，再重新启动dfs（执行start-dfs.sh）再执行jps命令可以看到datanode已正常启动。
出现该问题的原因：在第一次格式化dfs后，启动并使用了hadoop，后来又重新执行了格式化命令（hdfs namenode -format)，这时namenode的clusterID会重新生成，而datanode的clusterID 保持不变。
解决办法：
1.检查防火墙和selinux
2.hosts里不要有127.0.0.1指向机器名的解析存在，如“127.0.0.1 localhost”。
解决办法：
是因为hbase和hadoop里都有这个jar包，选择其一移除即可。
解决办法：
原来是Hadoop在刚启动的时候，还处在安全模式造成的。
[coder@h2 hadoop-0.20.2]$ bin/hadoop dfsadmin -safemode get Safe mode is ON [coder@h2 hadoop-0.20.2]$
可等Hadoop退出安全模式后再执行HBase命令，或者手动退出Hadoop的安全模式
[coder@h2 hadoop-0.20.2]$ bin/hadoop dfsadmin -safemode leaveSafe mode is OFF [coder@h2 hadoop-0.20.2]$
cd /usr/local/hadoop2/bin
./hadoop dfsadmin -safemode leave
解决办法：
解决办法：
./stop-all.sh
hadoop namenode -format
rm -rf /home/hadoop/tmp/dfs
./start-all.sh
rm -rf /home/hadoop/tmp
rm -rf /home/hadoop/dfs_data
rm -rf /home/hadoop/pids
rm -rf /home/hadoop/dfs_name
cd /usr/local/hadoop2/bin/
./hadoop namenode -format
closing ipc connection to master.kaiser.com/192.168.0.60:8020: Connection refused
Call From master.kaiser.com/192.168.0.60 to master.kaiser.com:8020 failed on connection exception: java.net.ConnectException:Connection refused
log：
2014-09-03 13:50:39,029 INFO org.apache.hadoop.hdfs.server.common.Storage: Lock on /home/hadoop/dfs_name/in_use.lock acquired by nodename 7582@master.kaiser.com
2014-09-03 13:50:39,032 WARN org.apache.hadoop.hdfs.server.namenode.FSNamesystem: Encountered exception loading fsp_w_picpath
java.io.IOException: NameNode is not formatted.
2014-09-03 13:50:39,141 FATAL org.apache.hadoop.hdfs.server.namenode.NameNode: Exception in namenode join
java.io.IOException: NameNode is not formatted.
hadoop.hbase.MasterNotRunningException: The node /hbase is not in ZooKeeper. It should have been written by the master.Check the value configured in 'zookeeper.znode.parent'. There could be a mismatch with the one configured in the master.
2013-04-13 17:13:17,374 INFO org.apache.hadoop.hbase.util.FSUtils: Waiting for dfs to exit safe mode... 2013-04-13 17:13:27,377 INFO org.apache.hadoop.hbase.util.FSUtils: Waiting for dfs to exit safe mode... 2013-04-13 17:13:37,386 INFO org.apache.hadoop.hbase.util.FSUtils: Waiting for dfs to exit safe mode... 2013-04-13 17:13:47,393 INFO org.apache.hadoop.hbase.util.FSUtils: Waiting for dfs to exit safe mode... 2013-04-13 17:13:57,395 INFO org.apache.hadoop.hbase.util.FSUtils: Waiting for dfs to exit safe mode... 2013-04-13 17:14:07,409 INFO org.apache.hadoop.hbase.util.FSUtils: Waiting for dfs to exit safe mode...
执行hbase程序orshell命令出现如下提示（./hbase shell）：
SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/usr/local/hbase-0.92.1/lib/slf4j-log4j12-1.5.8.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/usr/local/hadoop2-1.0.3/lib/slf4j-log4j12-1.4.3.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
WARN org.apache.hadoop.hdfs.server.datanode.DataNode: Problem connecting to server: tmaster.kaiser.com/192.168.0.63:9000
2014-06-18 20:34:59,622 FATAL org.apache.hadoop.hdfs.server.datanode.DataNode: Initialization failed for block pool Block pool
java.io.IOException: Incompatible clusterIDs in /usr/local/hadoop/hdfs/data: namenode clusterID = CID-af6f15aa-efdd-479b-bf55-77270058e4f7; datanode clusterID = CID-736d1968-8fd1-4bc4-afef-5c72354c39ce
at org.apache.hadoop.hdfs.server.datanode.DataStorage.doTransition(DataStorage.java:472)
at org.apache.hadoop.hdfs.server.datanode.DataStorage.recoverTransitionRead(DataStorage.java:225)
at org.apache.hadoop.hdfs.server.datanode.DataStorage.recoverTransitionRead(DataStorage.java:249)
at org.apache.hadoop.hdfs.server.datanode.DataNode.initStorage(DataNode.java:929)
at org.apache.hadoop.hdfs.server.datanode.DataNode.initBlockPool(DataNode.java:900)
at org.apache.hadoop.hdfs.server.datanode.BPOfferService.verifyAndSetNamespaceInfo(BPOfferService.java:274)
at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.connectToNNAndHandshake(BPServiceActor.java:220)
at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.run(BPServiceActor.java:815)
at java.lang.Thread.run(Thread.java:744)
从日志中可以看出，原因是因为datanode的clusterID 和 namenode的clusterID 不匹配。
regionserver.HRegionServer: Failed deleting my ephemeral node
java.io.IOException: No FileSystem for scheme: hdfs
hadoop：pache.hadoop.hdfs.server.blockmanagement.DatanodeManager: Unresolved datanode registration: hostname cannot be resolved
Hbase：Will not attempt to authenticate using SASL (unknown error)
