Commands Guide Manual

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Commands Guide

Table of contents

1 Overview............................................................................................................................ 3

1.1 Generic Options............................................................................................................ 3

2 User Commands ................................................................................................................4

2.1 archive ..........................................................................................................................4

2.2 distcp ............................................................................................................................4

2.3 fs .................................................................................................................................. 4

2.4 fsck ...............................................................................................................................4

2.5 fetchdt .......................................................................................................................... 5

2.6 jar .................................................................................................................................5

2.7 job ................................................................................................................................ 5

2.8 pipes .............................................................................................................................6

2.9 queue ............................................................................................................................7

2.10 version ........................................................................................................................7

2.11 CLASSNAME ........................................................................................................... 8

2.12 classpath .....................................................................................................................8

3 Administration Commands ............................................................................................... 8

3.1 balancer ........................................................................................................................8

3.2 daemonlog ....................................................................................................................8

3.3 datanode........................................................................................................................ 9

3.4 dfsadmin ...................................................................................................................... 9

3.5 mradmin...................................................................................................................... 10

3.6 jobtracker ................................................................................................................... 11

3.7 namenode ...................................................................................................................11

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3.8 secondarynamenode ...................................................................................................12

3.9 tasktracker ..................................................................................................................12

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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, job and fetchdt. 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 File System 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]]]

COMMAND_OPTION Description

<path> Start checking from this path.

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COMMAND_OPTION Description

-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 fetchdt

Gets Delegation Token from a NameNode. See fetchdt for more info.

Usage: hadoop fetchdt [GENERIC_OPTIONS] [--webservice

<namenode_http_addr>] <path>

COMMAND_OPTION Description

<fileName> File name to store the token into.

--webservice <https_address> use http protocol instead of RPC

2.6 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

2.7 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

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[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 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

2.8 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

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COMMAND_OPTION Description

-jobconf <key=value>,

<key=value>, ...

Add/override configuration for job

-input <path> Input directory

-output <path> Output directory

-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

2.9 queue

command to interact and view Job Queue information

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

showJobs]] | [-showacls]

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.

-showacls Displays the queue name and associated queue

operations allowed for the current user. The list

consists of only those queues to which the user has

access.

2.10 version

Prints the version.

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Usage: hadoop version

2.11 CLASSNAME

hadoop script can be used to invoke any class.

Usage: hadoop CLASSNAME

Runs the class named CLASSNAME.

2.12 classpath

Prints the class path needed to get the Hadoop jar and the required libraries.

Usage: hadoop classpath

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>

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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.

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.

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COMMAND_OPTION Description

-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

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 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.

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3.6 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.

3.7 namenode

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

Rollback

Usage: hadoop namenode [-format [-force] [-nonInteractive]] |

[-upgrade] | [-rollback] | [-finalize] | [-importCheckpoint]

COMMAND_OPTION Description

-format [-force] [-nonInteractive] Formats the namenode. It starts the namenode,

formats it and then shuts it down. User will be

prompted for input if the name directories exist on

the local filesystem.

-nonInteractive: User will not be prompted for input

if the name directories exist in the local filesystem

and the format will fail.

-force: formats the namenode and the user will

NOT be prompted to confirm formatting of name

directories in the local filesystem. If -nonInteractive

option is specified it will be ignored.

-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

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3.8 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.

3.9 tasktracker

Runs a MapReduce task Tracker node.

Usage: hadoop tasktracker

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