Hadoop has an option parsing framework that employs parsing generic options as well as running classes.
| COMMAND\_OPTIONS | Description |
|:---- |:---- |
| SHELL\_OPTIONS | The common set of shell options. These are documented on the [Commands Manual](../../hadoop-project-dist/hadoop-common/CommandsManual.html#Shell_Options) page. |
| GENERIC\_OPTIONS | The common set of options supported by multiple commands. See the Hadoop [Commands Manual](../../hadoop-project-dist/hadoop-common/CommandsManual.html#Generic_Options) for more information. |
| COMMAND COMMAND\_OPTIONS | Various commands with their options are described in the following sections. The commands have been grouped into [User Commands](#User_Commands) and [Administration Commands](#Administration_Commands). |
| `--jar`*path* | write classpath as manifest in jar named *path* |
| `-h`, `--help` | print help |
Prints the class path needed to get the Hadoop jar and the required libraries. If called without arguments, then prints the classpath set up by the command scripts, which is likely to contain wildcards in the classpath entries. Additional options print the classpath after wildcard expansion or write the classpath into the manifest of a jar file. The latter is useful in environments where wildcards cannot be used and the expanded classpath exceeds the maximum supported command line length.
Run a filesystem command on the file system supported in Hadoop. The various COMMAND\_OPTIONS can be found at [File System Shell Guide](../hadoop-common/FileSystemShell.html).
Runs the HDFS filesystem checking utility. See [fsck](./HdfsUserGuide.html#fsck) for more info.
### `getconf`
Usage:
hdfs getconf -namenodes
hdfs getconf -secondaryNameNodes
hdfs getconf -backupNodes
hdfs getconf -includeFile
hdfs getconf -excludeFile
hdfs getconf -nnRpcAddresses
hdfs getconf -confKey [key]
| COMMAND\_OPTION | Description |
|:---- |:---- |
| `-namenodes` | gets list of namenodes in the cluster. |
| `-secondaryNameNodes` | gets list of secondary namenodes in the cluster. |
| `-backupNodes` | gets list of backup nodes in the cluster. |
| `-includeFile` | gets the include file path that defines the datanodes that can join the cluster. |
| `-excludeFile` | gets the exclude file path that defines the datanodes that need to decommissioned. |
| `-nnRpcAddresses` | gets the namenode rpc addresses |
| `-confKey` [key] | gets a specific key from the configuration |
Gets configuration information from the configuration directory, post-processing.
### `groups`
Usage: `hdfs groups [username ...]`
Returns the group information given one or more usernames.
### `lsSnapshottableDir`
Usage: `hdfs lsSnapshottableDir [-help]`
| COMMAND\_OPTION | Description |
|:---- |:---- |
| `-help` | print help |
Get the list of snapshottable directories. When this is run as a super user, it returns all snapshottable directories. Otherwise it returns those directories that are owned by the current user.
| `-i`,`--inputFile` *arg* | edits file to process, xml (case insensitive) extension means XML format, any other filename means binary format |
| `-o`,`--outputFile` *arg* | Name of output file. If the specified file exists, it will be overwritten, format of the file is determined by -p option |
#### Optional command line arguments:
| COMMAND\_OPTION | Description |
|:---- |:---- |
| `-f`,`--fix-txids` | Renumber the transaction IDs in the input, so that there are no gaps or invalid transaction IDs. |
| `-h`,`--help` | Display usage information and exit |
| `-p`,`--processor` *arg* | Select which type of processor to apply against image file, currently supported processors are: binary (native binary format that Hadoop uses), xml (default, XML format), stats (prints statistics about edits file) |
| `-v`,`--verbose` | More verbose output, prints the input and output filenames, for processors that write to a file, also output to screen. On large image files this will dramatically increase processing time (default is false). |
| `-o`,`--outputFile` *output file* | Specify the output filename, if the specified output processor generates one. If the specified file already exists, it is silently overwritten. (output to stdout by default) If the input file is an XML file, it also creates an <outputFile>.md5. |
| `-p`,`--processor` *processor* | Specify the image processor to apply against the image file. Currently valid options are `Web` (default), `XML`, `Delimited`, `FileDistribution` and `ReverseXML`. |
| `-addr`*address* | Specify the address(host:port) to listen. (localhost:5978 by default). This option is used with Web processor. |
| `-maxSize`*size* | Specify the range [0, maxSize] of file sizes to be analyzed in bytes (128GB by default). This option is used with FileDistribution processor. |
| `-step`*size* | Specify the granularity of the distribution in bytes (2MB by default). This option is used with FileDistribution processor. |
| `-format` | Format the output result in a human-readable fashion rather than a number of bytes. (false by default). This option is used with FileDistribution processor. |
| `-delimiter`*arg* | Delimiting string to use with Delimited processor. |
| `-t`,`--temp` *temporary dir* | Use temporary dir to cache intermediate result to generate Delimited outputs. If not set, Delimited processor constructs the namespace in memory before outputting text. |
| `-h`,`--help` | Display the tool usage and help information and exit. |
| `-i`,`--inputFile` *input file* | Specify the input fsimage file to process. |
| `-o`,`--outputFile` *output file* | Specify the output filename, if the specified output processor generates one. If the specified file already exists, it is silently overwritten. |
| `-p`\|`--processor`*processor* | Specify the image processor to apply against the image file. Valid options are Ls (default), XML, Delimited, Indented, and FileDistribution. |
| `-maxSize`*size* | Specify the range [0, maxSize] of file sizes to be analyzed in bytes (128GB by default). This option is used with FileDistribution processor. |
| `-step`*size* | Specify the granularity of the distribution in bytes (2MB by default). This option is used with FileDistribution processor. |
| `-format` | Format the output result in a human-readable fashion rather than a number of bytes. (false by default). This option is used with FileDistribution processor. |
| `-skipBlocks` | Do not enumerate individual blocks within files. This may save processing time and outfile file space on namespaces with very large files. The Ls processor reads the blocks to correctly determine file sizes and ignores this option. |
| `-printToScreen` | Pipe output of processor to console as well as specified file. On extremely large namespaces, this may increase processing time by an order of magnitude. |
| `-delimiter`*arg* | When used in conjunction with the Delimited processor, replaces the default tab delimiter with the string specified by *arg*. |
| `-h`\|`--help` | Display the tool usage and help information and exit. |
Hadoop offline image viewer for older versions of Hadoop. See [oiv\_legacy Command](./HdfsImageViewer.html#oiv_legacy_Command) for more info.
Determine the difference between HDFS snapshots. See the [HDFS Snapshot Documentation](./HdfsSnapshots.html#Get_Snapshots_Difference_Report) for more information.
### `version`
Usage: `hdfs version`
Prints the version.
Administration Commands
-----------------------
Commands useful for administrators of a hadoop cluster.
| `-policy` \<policy\> | `datanode` (default): Cluster is balanced if each datanode is balanced.<br/>`blockpool`: Cluster is balanced if each block pool in each datanode is balanced. |
| `-threshold` \<threshold\> | Percentage of disk capacity. This overwrites the default threshold. |
| `-exclude -f` \<hosts-file\> \| \<comma-separated list of hosts\> | Excludes the specified datanodes from being balanced by the balancer. |
| `-include -f` \<hosts-file\> \| \<comma-separated list of hosts\> | Includes only the specified datanodes to be balanced by the balancer. |
| `-runDuringUpgrade` | Whether to run the balancer during an ongoing HDFS upgrade. This is usually not desired since it will not affect used space on over-utilized machines. |
| `-h`\|`--help` | Display the tool usage and help information and exit. |
Runs a cluster balancing utility. An administrator can simply press Ctrl-C to stop the rebalancing process. See [Balancer](./HdfsUserGuide.html#Balancer) for more details.
Note that the `blockpool` policy is more strict than the `datanode` policy.
Besides the above command options, a pinning feature is introduced starting from 2.7.0 to prevent certain replicas from getting moved by balancer/mover. This pinning feature is disabled by default, and can be enabled by configuration property "dfs.datanode.block-pinning.enabled". When enabled, this feature only affects blocks that are written to favored nodes specified in the create() call. This feature is useful when we want to maintain the data locality, for applications such as HBase regionserver.
| `-regular` | Normal datanode startup (default). |
| `-rollback` | Rollback the datanode to the previous version. This should be used after stopping the datanode and distributing the old hadoop version. |
| `-rollingupgrade` rollback | Rollback a rolling upgrade operation. |
| `-report``[-live]``[-dead]``[-decommissioning]` | Reports basic filesystem information and statistics, The dfs usage can be different from "du" usage, because it measures raw space used by replication, checksums, snapshots and etc. on all the DNs. Optional flags may be used to filter the list of displayed DataNodes. |
| `-safemode` enter\|leave\|get\|wait\|forceExit | Safe mode maintenance command. Safe mode is a Namenode state in which it <br/>1. does not accept changes to the name space (read-only) <br/>2. does not replicate or delete blocks. <br/>Safe mode is entered automatically at Namenode startup, and leaves safe mode automatically when the configured minimum percentage of blocks satisfies the minimum replication condition. If Namenode detects any anomaly then it will linger in safe mode till that issue is resolved. If that anomaly is the consequence of a deliberate action, then administrator can use -safemode forceExit to exit safe mode. The cases where forceExit may be required are<br/> 1. Namenode metadata is not consistent. If Namenode detects that metadata has been modified out of band and can cause data loss, then Namenode will enter forceExit state. At that point user can either restart Namenode with correct metadata files or forceExit (if data loss is acceptable).<br/>2. Rollback causes metadata to be replaced and rarely it can trigger safe mode forceExit state in Namenode. In that case you may proceed by issuing -safemode forceExit.<br/> Safe mode can also be entered manually, but then it can only be turned off manually as well. |
| `-saveNamespace``\[-beforeShutdown\]` | Save current namespace into storage directories and reset edits log. Requires safe mode. If the "beforeShutdown" option is given, the NameNode does a checkpoint if and only if no checkpoint has been done during a time window (a configurable number of checkpoint periods). This is usually used before shutting down the NameNode to prevent potential fsimage/editlog corruption. |
| `-rollEdits` | Rolls the edit log on the active NameNode. |
| `-restoreFailedStorage` true\|false\|check | This option will turn on/off automatic attempt to restore failed storage replicas. If a failed storage becomes available again the system will attempt to restore edits and/or fsimage during checkpoint. 'check' option will return current setting. |
| `-refreshNodes` | Re-read the hosts and exclude files to update the set of Datanodes that are allowed to connect to the Namenode and those that should be decommissioned or recommissioned. |
| `-setQuota` \<quota\> \<dirname\>...\<dirname\> | See [HDFS Quotas Guide](../hadoop-hdfs/HdfsQuotaAdminGuide.html#Administrative_Commands) for the detail. |
| `-clrQuota` \<dirname\>...\<dirname\> | See [HDFS Quotas Guide](../hadoop-hdfs/HdfsQuotaAdminGuide.html#Administrative_Commands) for the detail. |
| `-setSpaceQuota` \<quota\> `[-storageType <storagetype>]` \<dirname\>...\<dirname\> | See [HDFS Quotas Guide](../hadoop-hdfs/HdfsQuotaAdminGuide.html#Administrative_Commands) for the detail. |
| `-clrSpaceQuota``[-storageType <storagetype>]` \<dirname\>...\<dirname\> | See [HDFS Quotas Guide](../hadoop-hdfs/HdfsQuotaAdminGuide.html#Administrative_Commands) for the detail. |
| `-finalizeUpgrade` | Finalize upgrade of HDFS. Datanodes delete their previous version working directories, followed by Namenode doing the same. This completes the upgrade process. |
| `-rollingUpgrade` [\<query\>\|\<prepare\>\|\<finalize\>] | See [Rolling Upgrade document](../hadoop-hdfs/HdfsRollingUpgrade.html#dfsadmin_-rollingUpgrade) for the detail. |
| `-refreshServiceAcl` | Reload the service-level authorization policy file. |
| `-refreshSuperUserGroupsConfiguration` | Refresh superuser proxy groups mappings |
| `-refreshCallQueue` | Reload the call queue from config. |
| `-refresh` \<host:ipc\_port\> \<key\> [arg1..argn] | Triggers a runtime-refresh of the resource specified by \<key\> on \<host:ipc\_port\>. All other args after are sent to the host. |
| `-reconfig` \<datanode \|namenode\> \<host:ipc\_port\> \<start\|status\|properties\> | Starts reconfiguration or gets the status of an ongoing reconfiguration, or gets a list of reconfigurable properties. The second parameter specifies the node type. |
| `-printTopology` | Print a tree of the racks and their nodes as reported by the Namenode |
| `-refreshNamenodes` datanodehost:port | For the given datanode, reloads the configuration files, stops serving the removed block-pools and starts serving new block-pools. |
| `-deleteBlockPool` datanode-host:port blockpoolId [force] | If force is passed, block pool directory for the given blockpool id on the given datanode is deleted along with its contents, otherwise the directory is deleted only if it is empty. The command will fail if datanode is still serving the block pool. Refer to refreshNamenodes to shutdown a block pool service on a datanode. |
| `-setBalancerBandwidth` \<bandwidth in bytes per second\> | Changes the network bandwidth used by each datanode during HDFS block balancing. \<bandwidth\> is the maximum number of bytes per second that will be used by each datanode. This value overrides the dfs.balance.bandwidthPerSec parameter. NOTE: The new value is not persistent on the DataNode. |
| `-getBalancerBandwidth` \<datanode\_host:ipc\_port\> | Get the network bandwidth(in bytes per second) for the given datanode. This is the maximum network bandwidth used by the datanode during HDFS block balancing.|
| `-allowSnapshot` \<snapshotDir\> | Allowing snapshots of a directory to be created. If the operation completes successfully, the directory becomes snapshottable. See the [HDFS Snapshot Documentation](./HdfsSnapshots.html) for more information. |
| `-disallowSnapshot` \<snapshotDir\> | Disallowing snapshots of a directory to be created. All snapshots of the directory must be deleted before disallowing snapshots. See the [HDFS Snapshot Documentation](./HdfsSnapshots.html) for more information. |
| `-shutdownDatanode` \<datanode\_host:ipc\_port\> [upgrade] | Submit a shutdown request for the given datanode. See [Rolling Upgrade document](./HdfsRollingUpgrade.html#dfsadmin_-shutdownDatanode) for the detail. |
| `-evictWriters` \<datanode\_host:ipc\_port\> | Make the datanode evict all clients that are writing a block. This is useful if decommissioning is hung due to slow writers. |
| `-getDatanodeInfo` \<datanode\_host:ipc\_port\> | Get the information about the given datanode. See [Rolling Upgrade document](./HdfsRollingUpgrade.html#dfsadmin_-getDatanodeInfo) for the detail. |
| `-metasave` filename | Save Namenode's primary data structures to *filename* in the directory specified by hadoop.log.dir property. *filename* is overwritten if it exists. *filename* will contain one line for each of the following<br/>1. Datanodes heart beating with Namenode<br/>2. Blocks waiting to be replicated<br/>3. Blocks currently being replicated<br/>4. Blocks waiting to be deleted |
| `-triggerBlockReport``[-incremental]` \<datanode\_host:ipc\_port\> | Trigger a block report for the given datanode. If 'incremental' is specified, it will be otherwise, it will be a full block report. |
| `-help` [cmd] | Displays help for the given command or all commands if none is specified. |
See [HDFS HA with NFS](./HDFSHighAvailabilityWithNFS.html#Administrative_commands) or [HDFS HA with QJM](./HDFSHighAvailabilityWithQJM.html#Administrative_commands) for more information on this command.
### `journalnode`
Usage: `hdfs journalnode`
This comamnd starts a journalnode for use with [HDFS HA with QJM](./HDFSHighAvailabilityWithQJM.html#Administrative_commands).
In addition, a pinning feature is introduced starting from 2.7.0 to prevent certain replicas from getting moved by balancer/mover. This pinning feature is disabled by default, and can be enabled by configuration property "dfs.datanode.block-pinning.enabled". When enabled, this feature only affects blocks that are written to favored nodes specified in the create() call. This feature is useful when we want to maintain the data locality, for applications such as HBase regionserver.
| `-format``[-clusterid cid]``[-force]``[-nonInteractive]` | Formats the specified NameNode. It starts the NameNode, formats it and then shut it down. -force option formats if the name directory exists. -nonInteractive option aborts if the name directory exists, unless -force option is specified. |
| `-upgrade``[-clusterid cid]` [`-renameReserved` \<k-v pairs\>] | Namenode should be started with upgrade option after the distribution of new Hadoop version. |
| `-upgradeOnly``[-clusterid cid]` [`-renameReserved` \<k-v pairs\>] | Upgrade the specified NameNode and then shutdown it. |
| `-rollback` | Rollback the NameNode to the previous version. This should be used after stopping the cluster and distributing the old Hadoop version. |
| `-importCheckpoint` | Loads image from a checkpoint directory and save it into the current one. Checkpoint dir is read from property dfs.namenode.checkpoint.dir |
| `-initializeSharedEdits` | Format a new shared edits dir and copy in enough edit log segments so that the standby NameNode can start up. |
| `-bootstrapStandby` | Allows the standby NameNode's storage directories to be bootstrapped by copying the latest namespace snapshot from the active NameNode. This is used when first configuring an HA cluster. |
| `-recover``[-force]` | Recover lost metadata on a corrupt filesystem. See [HDFS User Guide](./HdfsUserGuide.html#Recovery_Mode) for the detail. |
| `-metadataVersion` | Verify that configured directories exist, then print the metadata versions of the software and the image. |
| `-checkpoint` [force] | Checkpoints the SecondaryNameNode if EditLog size \>= fs.checkpoint.size. If `force` is used, checkpoint irrespective of EditLog size. |
| `-format` | Format the local storage during startup. |
| `-geteditsize` | Prints the number of uncheckpointed transactions on the NameNode. |
Runs the HDFS secondary namenode. See [Secondary Namenode](./HdfsUserGuide.html#Secondary_NameNode) for more info.
This comamnd starts a Zookeeper Failover Controller process for use with [HDFS HA with QJM](./HDFSHighAvailabilityWithQJM.html#Administrative_commands).
Debug Commands
--------------
Useful commands to help administrators debug HDFS issues, like validating block files and calling recoverLease.
