Administration Commands

Commands useful for administrators of a hadoop cluster.

`balancer`

Runs a cluster balancing utility. An administrator can simply press Ctrl-C to stop the rebalancing process. See Rebalancer for more details.

Usage: hadoop balancer [-threshold <threshold>]

COMMAND_OPTION	Description
-threshold threshold	Percentage of disk capacity. This overwrites the default threshold.

`daemonlog`

Get/Set the log level for each daemon.

Usage: hadoop daemonlog -getlevel <host:port> <name> Usage: hadoop daemonlog -setlevel <host:port> <name> <level>

COMMAND_OPTION	Description
-getlevel host:port name	Prints the log level of the daemon running at host:port. This command internally connects to http://host:port/logLevel?log=name
-setlevel host:port name level	Sets the log level of the daemon running at host:port. This command internally connects to http://host:port/logLevel?log=name

`datanode`

Runs a HDFS datanode.

Usage: hadoop datanode [-rollback]

COMMAND_OPTION	Description
-rollback	Rollsback the datanode to the previous version. This should be used after stopping the datanode and distributing the old hadoop version.

`dfsadmin`

Runs a HDFS dfsadmin client.

COMMAND_OPTION	Description
-report	Reports basic filesystem information and statistics.
-safemode enter / leave / get / wait	Safe mode maintenance command. Safe mode is a Namenode state in which it 1. does not accept changes to the name space (read-only) 2. does not replicate or delete blocks. 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. Safe mode can also be entered manually, but then it can only be turned off manually as well.
-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.
-finalizeUpgrade	Finalize upgrade of HDFS. Datanodes delete their previous version working directories, followed by Namenode doing the same. This completes the upgrade process.
-upgradeProgress status / details / force	Request current distributed upgrade status, a detailed status or force the upgrade to proceed.
-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 1. Datanodes heart beating with Namenode 2. Blocks waiting to be replicated 3. Blocks currrently being replicated 4. Blocks waiting to be deleted
-setQuota quota dirname...dirname	Set the quota quota for each directory dirname. The directory quota is a long integer that puts a hard limit on the number of names in the directory tree. Best effort for the directory, with faults reported if 1. N is not a positive integer, or 2. user is not an administrator, or 3. the directory does not exist or is a file, or 4. the directory would immediately exceed the new quota.
-clrQuota dirname...dirname	Clear the quota for each directory dirname. Best effort for the directory. with fault reported if 1. the directory does not exist or is a file, or 2. user is not an administrator. It does not fault if the directory has no quota.
-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.
-help [cmd]	Displays help for the given command or all commands if none is specified.

`mradmin`

Runs MR admin client

Usage: hadoop mradmin [ GENERIC_OPTIONS ] [-refreshQueueAcls]

COMMAND_OPTION	Description
-refreshQueueAcls	Refresh the queue acls used by hadoop, to check access during submissions and administration of the job by the user. The properties present in mapred-queue-acls.xml is reloaded by the queue manager.

`jobtracker`

Runs the MapReduce job Tracker node.

Usage: hadoop jobtracker [-dumpConfiguration]

COMMAND_OPTION	Description
-dumpConfiguration	Dumps the configuration used by the JobTracker alongwith queue configuration in JSON format into Standard output used by the jobtracker and exits.

`namenode`

Runs the namenode. More info about the upgrade, rollback and finalize is at Upgrade Rollback.

Usage: hadoop namenode [-format] | [-upgrade] | [-rollback] | [-finalize] | [-importCheckpoint]

COMMAND_OPTION	Description
-format	Formats the namenode. It starts the namenode, formats it and then shut it down.
-upgrade	Namenode should be started with upgrade option after the distribution of new hadoop version.
-rollback	Rollsback the namenode to the previous version. This should be used after stopping the cluster and distributing the old hadoop version.
-finalize	Finalize will remove the previous state of the files system. Recent upgrade will become permanent. Rollback option will not be available anymore. After finalization it shuts the namenode down.
-importCheckpoint	Loads image from a checkpoint directory and save it into the current one. Checkpoint dir is read from property fs.checkpoint.dir

`secondarynamenode`

Runs the HDFS secondary namenode. See Secondary Namenode for more info.

Usage: hadoop secondarynamenode [-checkpoint [force]] | [-geteditsize]

COMMAND_OPTION	Description
-checkpoint [-force]	Checkpoints the Secondary namenode if EditLog size >= fs.checkpoint.size. If `-force` is used, checkpoint irrespective of EditLog size.
-geteditsize	Prints the EditLog size.

`tasktracker`

Runs a MapReduce task Tracker node.

Usage: hadoop tasktracker