之前集群能够启动各个节点的。
因为最近集群改名了，启动NameNode可以的。
启动DataNode没有任何提示。
进入hadoop logs目录查找hadoop-root-datanode-bd-cluster1.log文件发现下面的错误。
错误关键信息： org.apache.hadoop.hdfs.server.common.Storage: Failed to add storage directory [DISK]file:/tmp/hadoop-root/dfs/data
java.io.IOException: Incompatible clusterIDs in /tmp/hadoop-root/dfs/data: namenode clusterID = CID-17d9d128-d0f2-4b73-9460-0074536fa7a7; datanode clusterID = CID-29c3283b-0f02-4814-ae01-50065e15c004
2021-05-15 15:34:23,573 INFO org.apache.hadoop.hdfs.server.datanode.DataNode: Acknowledging ACTIVE Namenode during handshakeBlock pool (Datanode Uuid unassigned) service to /10.231.33.101:9000
2021-05-15 15:34:23,582 INFO org.apache.hadoop.hdfs.server.common.Storage: Using 1 threads to upgrade data directories (dfs.datanode.parallel.volumes.load.threads.num=1, dataDirs=1)
2021-05-15 15:34:23,597 INFO org.apache.hadoop.hdfs.server.common.Storage: Lock on /tmp/hadoop-root/dfs/data/in_use.lock acquired by nodename 5526@bd-cluster1
2021-05-15 15:34:23,600 WARN org.apache.hadoop.hdfs.server.common.Storage: Failed to add storage directory [DISK]file:/tmp/hadoop-root/dfs/data
java.io.IOException: Incompatible clusterIDs in /tmp/hadoop-root/dfs/data: namenode clusterID = CID-17d9d128-d0f2-4b73-9460-0074536fa7a7; datanode clusterID = CID-29c3283b-0f02-4814-ae01-50065e15c004
at org.apache.hadoop.hdfs.server.datanode.DataStorage.doTransition(DataStorage.java:744)
at org.apache.hadoop.hdfs.server.datanode.DataStorage.loadStorageDirectory(DataStorage.java:294)
at org.apache.hadoop.hdfs.server.datanode.DataStorage.loadDataStorage(DataStorage.java:407)
at org.apache.hadoop.hdfs.server.datanode.DataStorage.addStorageLocations(DataStorage.java:387)
at org.apache.hadoop.hdfs.server.datanode.DataStorage.recoverTransitionRead(DataStorage.java:559)
at org.apache.hadoop.hdfs.server.datanode.DataNode.initStorage(DataNode.java:1743)
at org.apache.hadoop.hdfs.server.datanode.DataNode.initBlockPool(DataNode.java:1679)
at org.apache.hadoop.hdfs.server.datanode.BPOfferService.verifyAndSetNamespaceInfo(BPOfferService.java:390)
at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.connectToNNAndHandshake(BPServiceActor.java:282)
at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.run(BPServiceActor.java:824)
at java.lang.Thread.run(Thread.java:748)
2021-05-15 15:34:23,602 ERROR org.apache.hadoop.hdfs.server.datanode.DataNode: Initialization failed for Block pool (Datanode Uuid f4005613-8a0d-4177-a59a-5a999f41ccd6) service to /10.231.33.101:9000. Exiting.
java.io.IOException: All specified directories have failed to load.
at org.apache.hadoop.hdfs.server.datanode.DataStorage.recoverTransitionRead(DataStorage.java:560)
at org.apache.hadoop.hdfs.server.datanode.DataNode.initStorage(DataNode.java:1743)
at org.apache.hadoop.hdfs.server.datanode.DataNode.initBlockPool(DataNode.java:1679)
at org.apache.hadoop.hdfs.server.datanode.BPOfferService.verifyAndSetNamespaceInfo(BPOfferService.java:390)
at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.connectToNNAndHandshake(BPServiceActor.java:282)
at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.run(BPServiceActor.java:824)
at java.lang.Thread.run(Thread.java:748)
2021-05-15 15:34:23,603 WARN org.apache.hadoop.hdfs.server.datanode.DataNode: Ending block pool service for: Block pool (Datanode Uuid f4005613-8a0d-4177-a59a-5a999f41ccd6) service to /10.231.33.101:9000
分析
上面的错误就是因为本地的DataNode之前存储过旧集群数据，写新数据的时候发现版本不一样。
直接删除旧的DataNode的数据目录, 默认为：/tmp/hadoop-root/dfs/data.
重新运行：hdfs --daemon start datanode
启动成功了：datanode连接成功。
好了，如果有多个DataNode必须重复删除所有DataNode的数据文件，再运行上述命令。
总结
根本原因：不同集群数据问题校验问题，错误为Incompatible clusterIDs错误
