MapReduce Commands Guide

Overview

All mapreduce commands are invoked by the bin/mapred script. Running the mapred script without any arguments prints the description for all commands.

Usage: mapred [SHELL_OPTIONS] COMMAND [GENERIC_OPTIONS] [COMMAND_OPTIONS]

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 Hadoop Commands Reference page.
GENERIC_OPTIONS	The common set of options supported by multiple commands. See the Hadoop Commands Reference for more information.
COMMAND_OPTIONS	Various commands with their options are described in the following sections. The commands have been grouped into User Commands and Administration Commands.

User Commands

Commands useful for users of a hadoop cluster.

`archive`

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

`archive-logs`

A tool to combine YARN aggregated logs into Hadoop archives to reduce the number of files in HDFS. More information can be found at Hadoop Archive Logs Guide.

`classpath`

Usage: yarn classpath [--glob |--jar <path> |-h |--help]

COMMAND_OPTION	Description
`--glob`	expand wildcards
`--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.

`distcp`

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

`job`

Command to interact with Map Reduce Jobs.

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] *jobHistoryFile	jobId* [-outfile file] [-format *human
-list [all]	Displays jobs which are yet to complete. `-list all` displays all jobs.
-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
-list-active-trackers	List all the active NodeManagers in the cluster.
-list-blacklisted-trackers	List the black listed task trackers in the cluster. This command is not supported in MRv2 based cluster.
-list-attempt-ids job-id task-type task-state	List the attempt-ids based on the task type and the status given. Valid values for task-type are REDUCE, MAP. Valid values for task-state are running, pending, completed, failed, killed.
-logs job-id task-attempt-id	Dump the container log for a job if taskAttemptId is not specified, otherwise dump the log for the task with the specified taskAttemptId. The logs will be dumped in system out.
-config job-id file	Download the job configuration file.

`pipes`

Runs a pipes job.

Usage: mapred 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
-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

`queue`

command to interact and view Job Queue information

Usage: mapred 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.

`version`

Prints the version.

Usage: mapred version

`envvars`

Usage: mapred envvars

Display computed Hadoop environment variables.

Administration Commands

Commands useful for administrators of a hadoop cluster.

`historyserver`

Start JobHistoryServer.

Usage: mapred historyserver

`hsadmin`

Runs a MapReduce hsadmin client for execute JobHistoryServer administrative commands.

COMMAND_OPTION	Description
-refreshUserToGroupsMappings	Refresh user-to-groups mappings
-refreshSuperUserGroupsConfiguration	Refresh superuser proxy groups mappings
-refreshAdminAcls	Refresh acls for administration of Job history server
-refreshLoadedJobCache	Refresh loaded job cache of Job history server
-refreshJobRetentionSettings	Refresh job history period, job cleaner settings
-refreshLogRetentionSettings	Refresh log retention period and log retention check interval
-getGroups [username]	Get the groups which given user belongs to
-help [cmd]	Displays help for the given command or all commands if none is specified.

`frameworkuploader`

Collects framework jars and uploads them to HDFS as a tarball.

Usage: mapred frameworkuploader -target <target> [-fs <filesystem>] [-input <classpath>] [-blacklist <list>] [-whitelist <list>] [-initialReplication <num>] [-acceptableReplication <num>] [-finalReplication <num>] [-timeout <seconds>] [-nosymlink]

COMMAND_OPTION	Description
-input classpath	This is the input classpath that is searched for jar files to be included in the tarball.
-fs filesystem	The target file system. Defaults to the default filesystem set by fs.defaultFS.
-target target	This is the target location of the framework tarball, optionally followed by a # with the localized alias. An example would be /usr/lib/framework.tar#framework. Make sure the target directory is readable by all users but it is not writable by others than administrators to protect cluster security.
-blacklist list	This is a comma separated regex array to filter the jar file names to exclude from the class path. It can be used for example to exclude test jars or Hadoop services that are not necessary to localize.
-whitelist list	This is a comma separated regex array to include certain jar files. This can be used to provide additional security, so that no external source can include malicious code in the classpath when the tool runs.
-nosymlink	This flag can be used to exclude symlinks that point to the same directory. This is not widely used. For example, `/a/foo.jar` and a symlink `/a/bar.jar` that points to `/a/foo.jar` would normally add `foo.jar` and `bar.jar` to the tarball as separate files despite them actually being the same file. This flag would make the tool exclude `/a/bar.jar` so only one copy of the file is added.
-initialReplication num	This is the replication count that the framework tarball is created with. It is safe to leave this value at the default 3. This is the tested scenario.
-finalReplication num	The uploader tool sets the replication once all blocks are collected and uploaded. If quick initial startup is required, then it is advised to set this to the commissioned node count divided by two but not more than 512.
-acceptableReplication num	The tool will wait until the tarball has been replicated this number of times before exiting. This should be a replication count less than or equal to the value in `finalReplication`. This is typically a 90% of the value in `finalReplication` to accomodate failing nodes.
-timeout seconds	A timeout in seconds to wait to reach `acceptableReplication` before the tool exits. The tool logs an error otherwise and returns.