执行NameNode格式化时，运行 hdfs namenode -format 报错：
java.io.IOException: Cannot remove current directory: /home/bigdata/Opt/hadoop-2.10.1/tmp/dfs/name/current
报错原因是，之前已经执行NameNode格式化成功过。
解决办法：
使用root权限删除格式化NameNode时产生的current目录，再次执行格式化NameNode命令。
1、使用root登录
su root
2、删除/home/bigdata/Opt/hadoop-2.10.1/tmp/dfs/name目录下的current文件夹
进入目录/home/bigdata/Opt/hadoop-2.10.1/tmp/dfs/name
cd /home/bigdata/Opt/hadoop-2.10.1/tmp/dfs/name
可以看到该目录下有一个current文件夹
执行 rm -rf current 删除该文件夹后再通过ls查看目录可以看到已经删除了current
再重新执行格式化命令hdfs namenode -format 就可以了
[root@localhost name]# rm -rf current [root@localhost name]# ls [root@localhost name]# hdfs namenode -format 22/04/26 02:45:55 INFO namenode.NameNode: STARTUP_MSG: 22/04/26 02:45:55 INFO namenode.NameNode: registered UNIX signal handlers for [TERM, HUP, INT] 22/04/26 02:45:55 INFO namenode.NameNode: createNameNode [-format] Formatting using clusterid: CID-c569564d-3577-4097-acc9-43a3c95ca571 22/04/26 02:45:56 INFO namenode.FSEditLog: Edit logging is async:true 22/04/26 02:45:56 INFO namenode.FSNamesystem: KeyProvider: null 22/04/26 02:45:56 INFO namenode.FSNamesystem: fsLock is fair: true 22/04/26 02:45:56 INFO namenode.FSNamesystem: Detailed lock hold time metrics enabled: false 22/04/26 02:45:56 INFO namenode.FSNamesystem: fsOwner = root (auth:SIMPLE) 22/04/26 02:45:56 INFO namenode.FSNamesystem: supergroup = supergroup 22/04/26 02:45:56 INFO namenode.FSNamesystem: isPermissionEnabled = true 22/04/26 02:45:56 INFO namenode.FSNamesystem: HA Enabled: false 22/04/26 02:45:56 INFO common.Util: dfs.datanode.fileio.profiling.sampling.percentage set to 0. Disabling file IO profiling 22/04/26 02:45:56 INFO blockmanagement.DatanodeManager: dfs.block.invalidate.limit: configured=1000, counted=60, effected=1000 22/04/26 02:45:56 INFO blockmanagement.DatanodeManager: dfs.namenode.datanode.registration.ip-hostname-check=true 22/04/26 02:45:56 INFO blockmanagement.BlockManager: dfs.namenode.startup.delay.block.deletion.sec is set to 000:00:00:00.000 22/04/26 02:45:56 INFO blockmanagement.BlockManager: The block deletion will start around 2022 Apr 26 02:45:56 22/04/26 02:45:56 INFO util.GSet: Computing capacity for map BlocksMap 22/04/26 02:45:56 INFO util.GSet: VM type = 64-bit 22/04/26 02:45:56 INFO util.GSet: 2.0% max memory 889 MB = 17.8 MB 22/04/26 02:45:56 INFO util.GSet: capacity = 2^21 = 2097152 entries 22/04/26 02:45:56 INFO blockmanagement.BlockManager: dfs.block.access.token.enable=false 22/04/26 02:45:56 WARN conf.Configuration: No unit for dfs.heartbeat.interval(3) assuming SECONDS 22/04/26 02:45:56 WARN conf.Configuration: No unit for dfs.namenode.safemode.extension(30000) assuming MILLISECONDS 22/04/26 02:45:56 INFO blockmanagement.BlockManagerSafeMode: dfs.namenode.safemode.threshold-pct = 0.9990000128746033 22/04/26 02:45:56 INFO blockmanagement.BlockManagerSafeMode: dfs.namenode.safemode.min.datanodes = 0 22/04/26 02:45:56 INFO blockmanagement.BlockManagerSafeMode: dfs.namenode.safemode.extension = 30000 22/04/26 02:45:56 INFO blockmanagement.BlockManager: defaultReplication = 1 22/04/26 02:45:56 INFO blockmanagement.BlockManager: maxReplication = 512 22/04/26 02:45:56 INFO blockmanagement.BlockManager: minReplication = 1 22/04/26 02:45:56 INFO blockmanagement.BlockManager: maxReplicationStreams = 2 22/04/26 02:45:56 INFO blockmanagement.BlockManager: replicationRecheckInterval = 3000 22/04/26 02:45:56 INFO blockmanagement.BlockManager: encryptDataTransfer = false 22/04/26 02:45:56 INFO blockmanagement.BlockManager: maxNumBlocksToLog = 1000 22/04/26 02:45:56 INFO namenode.FSNamesystem: Append Enabled: true 22/04/26 02:45:56 INFO namenode.FSDirectory: GLOBAL serial map: bits=24 maxEntries=16777215 22/04/26 02:45:56 INFO util.GSet: Computing capacity for map INodeMap 22/04/26 02:45:56 INFO util.GSet: VM type = 64-bit 22/04/26 02:45:56 INFO util.GSet: 1.0% max memory 889 MB = 8.9 MB 22/04/26 02:45:56 INFO util.GSet: capacity = 2^20 = 1048576 entries 22/04/26 02:45:56 INFO namenode.FSDirectory: ACLs enabled? false 22/04/26 02:45:56 INFO namenode.FSDirectory: XAttrs enabled? true 22/04/26 02:45:56 INFO namenode.NameNode: Caching file names occurring more than 10 times 22/04/26 02:45:56 INFO snapshot.SnapshotManager: Loaded config captureOpenFiles: falseskipCaptureAccessTimeOnlyChange: false 22/04/26 02:45:56 INFO util.GSet: Computing capacity for map cachedBlocks 22/04/26 02:45:56 INFO util.GSet: VM type = 64-bit 22/04/26 02:45:56 INFO util.GSet: 0.25% max memory 889 MB = 2.2 MB 22/04/26 02:45:56 INFO util.GSet: capacity = 2^18 = 262144 entries 22/04/26 02:45:56 INFO metrics.TopMetrics: NNTop conf: dfs.namenode.top.window.num.buckets = 10 22/04/26 02:45:56 INFO metrics.TopMetrics: NNTop conf: dfs.namenode.top.num.users = 10 22/04/26 02:45:56 INFO metrics.TopMetrics: NNTop conf: dfs.namenode.top.windows.minutes = 1,5,25 22/04/26 02:45:56 INFO namenode.FSNamesystem: Retry cache on namenode is enabled 22/04/26 02:45:56 INFO namenode.FSNamesystem: Retry cache will use 0.03 of total heap and retry cache entry expiry time is 600000 millis 22/04/26 02:45:56 INFO util.GSet: Computing capacity for map NameNodeRetryCache 22/04/26 02:45:56 INFO util.GSet: VM type = 64-bit 22/04/26 02:45:56 INFO util.GSet: 0.029999999329447746% max memory 889 MB = 273.1 KB 22/04/26 02:45:56 INFO util.GSet: capacity = 2^15 = 32768 entries 22/04/26 02:45:56 INFO namenode.FSImage: Allocated new BlockPoolId: BP-3891196-127.0.0.1-1650966356523 22/04/26 02:45:56 INFO common.Storage: Storage directory /home/bigdata/Opt/hadoop-2.10.1/tmp/dfs/name has been successfully formatted. 22/04/26 02:45:56 INFO namenode.FSImageFormatProtobuf: Saving image file /home/bigdata/Opt/hadoop-2.10.1/tmp/dfs/name/current/fsimage.ckpt_0000000000000000000 using no compression 22/04/26 02:45:57 INFO namenode.FSImageFormatProtobuf: Image file /home/bigdata/Opt/hadoop-2.10.1/tmp/dfs/name/current/fsimage.ckpt_0000000000000000000 of size 323 bytes saved in 0 seconds . 22/04/26 02:45:57 INFO namenode.NNStorageRetentionManager: Going to retain 1 images with txid >= 0 22/04/26 02:45:57 INFO namenode.FSImage: FSImageSaver clean checkpoint: txid = 0 when meet shutdown. 22/04/26 02:45:57 INFO namenode.NameNode: SHUTDOWN_MSG:
