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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_OPTIONDescription
-threshold thresholdPercentage 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_OPTIONDescription
-getlevel host:port namePrints 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 levelSets 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_OPTIONDescription
-rollbackRollsback 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.

Usage: hadoop dfsadmin [GENERIC_OPTIONS] [-report] [-safemode enter | leave | get | wait] [-refreshNodes] [-finalizeUpgrade] [-upgradeProgress status | details | force] [-metasave filename] [-setQuota <quota> <dirname>...<dirname>] [-clrQuota <dirname>...<dirname>] [-restoreFailedStorage true|false|check] [-help [cmd]]

COMMAND_OPTIONDescription
-reportReports basic filesystem information and statistics.
-safemode enter / leave / get / waitSafe 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.
-refreshNodesRe-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.
-finalizeUpgradeFinalize upgrade of HDFS. Datanodes delete their previous version working directories, followed by Namenode doing the same. This completes the upgrade process.
-upgradeProgress status / details / forceRequest current distributed upgrade status, a detailed status or force the upgrade to proceed.
-metasave filenameSave 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...dirnameSet 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...dirnameClear 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 / checkThis 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_OPTIONDescription
-refreshQueueAclsRefresh 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_OPTIONDescription
-dumpConfigurationDumps 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_OPTIONDescription
-formatFormats the namenode. It starts the namenode, formats it and then shut it down.
-upgradeNamenode should be started with upgrade option after the distribution of new hadoop version.
-rollbackRollsback the namenode to the previous version. This should be used after stopping the cluster and distributing the old hadoop version.
-finalizeFinalize 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.
-importCheckpointLoads 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_OPTIONDescription
-checkpoint [-force]Checkpoints the Secondary namenode if EditLog size >= fs.checkpoint.size. If -force is used, checkpoint irrespective of EditLog size.
-geteditsizePrints the EditLog size.

tasktracker

Runs a MapReduce task Tracker node.

Usage: hadoop tasktracker