Commands Manual

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Commands Guide

Table of contents

1Overview............................................................................................................................2

1.1 Generic Options.............................................................................................................2

2User Commands ................................................................................................................3

2.1 archive .......................................................................................................................... 3

2.2 distcp .............................................................................................................................3

2.3 fs ................................................................................................................................... 3

2.4 fsck ............................................................................................................................... 3

2.5 jar ..................................................................................................................................4

2.6 job .................................................................................................................................4

2.7 pipes ..............................................................................................................................5

2.8 queue .............................................................................................................................6

2.9 version .......................................................................................................................... 6

2.10 CLASSNAME ............................................................................................................ 6

3Administration Commands ............................................................................................... 7

3.1 balancer .........................................................................................................................7

3.2 daemonlog .................................................................................................................... 7

3.3 datanode.........................................................................................................................7

3.4 dfsadmin ....................................................................................................................... 8

3.5 jobtracker ......................................................................................................................9

3.6 namenode ......................................................................................................................9

3.7 secondarynamenode ................................................................................................... 10

3.8 tasktracker ...................................................................................................................10

1. Overview

All hadoop commands are invoked by the bin/hadoop script. Running the hadoop script

without any arguments prints the description for all commands.

Usage: hadoop [--config confdir] [COMMAND] [GENERIC_OPTIONS]

[COMMAND_OPTIONS]

Hadoop has an option parsing framework that employs parsing generic options as well as

running classes.

COMMAND_OPTION Description

--config confdir Overwrites the default Configuration directory.

Default is ${HADOOP_HOME}/conf.

GENERIC_OPTIONS The common set of options supported by

multiple commands.

COMMAND

COMMAND_OPTIONS

Various commands with their options are

described in the following sections. The

commands have been grouped into User

Commands and Administration Commands.

1.1. Generic Options

The following options are supported by dfsadmin,fs,fsck and job. Applications should

implement Tool to support GenericOptions.

GENERIC_OPTION Description

-conf <configuration file> Specify an application configuration file.

-D <property=value> Use value for given property.

-fs <local|namenode:port> Specify a namenode.

-jt <local|jobtracker:port> Specify a job tracker. Applies only to job.

-files <comma separated list of

files>

Specify comma separated files to be copied to

the map reduce cluster. Applies only to job.

-libjars <comma seperated list of

jars>

Specify comma separated jar files to include in

the classpath. Applies only to job.

-archives <comma separated list of

archives>

Specify comma separated archives to be

unarchived on the compute machines. Applies

only to job.

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2. User Commands

Commands useful for users of a hadoop cluster.

2.1. archive

Creates a hadoop archive. More information can be found at Hadoop Archives.

Usage: hadoop archive -archiveName NAME <src>* <dest>

COMMAND_OPTION Description

-archiveName NAME Name of the archive to be created.

src Filesystem pathnames which work as usual with

regular expressions.

dest Destination directory which would contain the

archive.

2.2. distcp

Copy file or directories recursively. More information can be found at Hadoop DistCp Guide.

Usage: hadoop distcp <srcurl> <desturl>

COMMAND_OPTION Description

srcurl Source Url

desturl Destination Url

2.3. fs

Usage: hadoop fs [GENERIC_OPTIONS] [COMMAND_OPTIONS]

Runs a generic filesystem user client.

The various COMMAND_OPTIONS can be found at Hadoop FS Shell Guide.

2.4. fsck

Runs a HDFS filesystem checking utility. See Fsck for more info.

Usage: hadoop fsck [GENERIC_OPTIONS] <path> [-move | -delete |

-openforwrite] [-files [-blocks [-locations | -racks]]]

Commands Guide

COMMAND_OPTION Description

<path> Start checking from this path.

-move Move corrupted files to /lost+found

-delete Delete corrupted files.

-openforwrite Print out files opened for write.

-files Print out files being checked.

-blocks Print out block report.

-locations Print out locations for every block.

-racks Print out network topology for data-node

locations.

2.5. jar

Runs a jar file. Users can bundle their Map Reduce code in a jar file and execute it using this

command.

Usage: hadoop jar <jar> [mainClass] args...

The streaming jobs are run via this command. Examples can be referred from Streaming

examples

Word count example is also run using jar command. It can be referred from Wordcount

example

2.6. job

Command to interact with Map Reduce Jobs.

Usage: hadoop job [GENERIC_OPTIONS] [-submit <job-file>] |

[-status <job-id>] | [-counter <job-id> <group-name>

<counter-name>] | [-kill <job-id>] | [-events <job-id>

<from-event-#> <#-of-events>] | [-history [all]

<jobOutputDir>] | [-list [all]] | [-kill-task <task-id>] |

[-fail-task <task-id>] | [-set-priority <job-id> <priority>]

COMMAND_OPTION Description

-submit <job-file> Submits the job.

-status <job-id> Prints the map and reduce completion

Commands Guide

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percentage and all job counters.

-counter <job-id> <group-name>

<counter-name>

Prints the counter value.

-kill <job-id> Kills the job.

-events <job-id> <from-event-#>

<#-of-events>

Prints the events' details received by jobtracker

for the given range.

-history [all] <jobOutputDir> -history <jobOutputDir> prints job details, failed

and killed tip details. More details about the job

such as successful tasks and task attempts

made for each task can be viewed by specifying

the [all] option.

-list [all] -list all displays all jobs. -list displays only jobs

which are yet to complete.

-kill-task <task-id> Kills the task. Killed tasks are NOT counted

against failed attempts.

-fail-task <task-id> Fails the task. Failed tasks are counted against

failed attempts.

-set-priority <job-id> <priority> Changes the priority of the job. Allowed priority

values are VERY_HIGH, HIGH, NORMAL,

LOW, VERY_LOW

2.7. pipes

Runs a pipes job.

Usage: hadoop pipes [-conf <path>] [-jobconf <key=value>,

<key=value>, ...] [-input <path>] [-output <path>] [-jar <jar

file>] [-inputformat <class>] [-map <class>] [-partitioner

<class>] [-reduce <class>] [-writer <class>] [-program

<executable>] [-reduces <num>]

COMMAND_OPTION Description

-conf <path> Configuration for job

-jobconf <key=value>, <key=value>,

...

Add/override configuration for job

-input <path> Input directory

-output <path> Output directory

Commands Guide

-jar <jar file> Jar filename

-inputformat <class> InputFormat class

-map <class> Java Map class

-partitioner <class> Java Partitioner

-reduce <class> Java Reduce class

-writer <class> Java RecordWriter

-program <executable> Executable URI

-reduces <num> Number of reduces

2.8. queue

command to interact and view Job Queue information

Usage : hadoop queue [-list] | [-info <job-queue-name>

[-showJobs]]

COMMAND_OPTION Description

-list Gets list of Job Queues configured in the

system. Along with scheduling information

associated with the job queues.

-info <job-queue-name> [-showJobs] Displays the job queue information and

associated scheduling information of particular

job queue. If -showJobs options is present a list

of jobs submitted to the particular job queue is

displayed.

2.9. version

Prints the version.

Usage: hadoop version

2.10. CLASSNAME

hadoop script can be used to invoke any class.

Usage: hadoop CLASSNAME

Runs the class named CLASSNAME.

Commands Guide

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3. Administration Commands

Commands useful for administrators of a hadoop cluster.

3.1. 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.

3.2. 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>

3.3. 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.

Commands Guide

3.4. 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>] [-help [cmd]]

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> will contain

one line for each of the following

1. Datanodes heart beating with Namenode

2. Blocks waiting to be replicated

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3. Blocks currrently being replicated

4. Blocks waiting to be deleted

-setQuota <quota>

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.

-help [cmd] Displays help for the given command or all

commands if none is specified.

3.5. jobtracker

Runs the MapReduce job Tracker node.

Usage: hadoop jobtracker

3.6. 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

Commands Guide

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

3.7. 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.

3.8. tasktracker

Runs a MapReduce task Tracker node.

Usage: hadoop tasktracker

Commands Guide

Page 10

Commands Manual

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