hadoop/hadoop-common-project/hadoop-common/src/site/markdown/CommandsManual.md

Hadoop Commands Guide

Overview

All of the Hadoop commands and subprojects follow the same basic structure:

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

FIELD	Description
shellcommand	The command of the project being invoked. For example, Hadoop common uses hadoop, HDFS uses hdfs, and YARN uses yarn.
SHELL_OPTIONS	Options that the shell processes prior to executing Java.
COMMAND	Action to perform.
GENERIC_OPTIONS	The common set of options supported by multiple commands.
COMMAND_OPTIONS	Various commands with their options are described in this documention for the Hadoop common sub-project. HDFS and YARN are covered in other documents.

Shell Options

All of the shell commands will accept a common set of options. For some commands, these options are ignored. For example, passing ---hostnames on a command that only executes on a single host will be ignored.

SHELL_OPTION	Description
--buildpaths	Enables developer versions of jars.
--config confdir	Overwrites the default Configuration directory. Default is $HADOOP_HOME/etc/hadoop.
--daemon mode	If the command supports daemonization (e.g., hdfs namenode), execute in the appropriate mode. Supported modes are start to start the process in daemon mode, stop to stop the process, and status to determine the active status of the process. status will return an LSB-compliant result code. If no option is provided, commands that support daemonization will run in the foreground. For commands that do not support daemonization, this option is ignored.
--debug	Enables shell level configuration debugging information
--help	Shell script usage information.
--hostnames	When --slaves is used, override the slaves file with a space delimited list of hostnames where to execute a multi-host subcommand. If --slaves is not used, this option is ignored.
--hosts	When --slaves is used, override the slaves file with another file that contains a list of hostnames where to execute a multi-host subcommand. If --slaves is not used, this option is ignored.
--loglevel loglevel	Overrides the log level. Valid log levels are FATAL, ERROR, WARN, INFO, DEBUG, and TRACE. Default is INFO.
--slaves	If possible, execute this command on all hosts in the slaves file.

Generic Options

Many subcommands honor a common set of configuration options to alter their behavior:

GENERIC_OPTION	Description
-archives <comma separated list of archives>	Specify comma separated archives to be unarchived on the compute machines. Applies only to job.
-conf <configuration file>	Specify an application configuration file.
-D <property>=<value>	Use value for given property.
-files <comma separated list of files>	Specify comma separated files to be copied to the map reduce cluster. Applies only to job.
-jt <local> or <resourcemanager:port>	Specify a ResourceManager. Applies only to job.
-libjars <comma seperated list of jars>	Specify comma separated jar files to include in the classpath. Applies only to job.

Hadoop Common Commands

All of these commands are executed from the hadoop shell command. They have been broken up 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.

checknative

Usage: hadoop checknative [-a] [-h]

COMMAND_OPTION	Description
-a	Check all libraries are available.
-h	print help

This command checks the availability of the Hadoop native code. See Native Libaries for more information. By default, this command only checks the availability of libhadoop.

classpath

Usage: hadoop 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.

credential

Usage: hadoop credential <subcommand> [options]

COMMAND_OPTION	Description
create alias [-provider provider-path]	Prompts the user for a credential to be stored as the given alias. The hadoop.security.credential.provider.path within the core-site.xml file will be used unless a -provider is indicated.
delete alias [-provider provider-path] [-f]	Deletes the credential with the provided alias. The hadoop.security.credential.provider.path within the core-site.xml file will be used unless a -provider is indicated. The command asks for confirmation unless -f is specified
list [-provider provider-path]	Lists all of the credential aliases The hadoop.security.credential.provider.path within the core-site.xml file will be used unless a -provider is indicated.

Command to manage credentials, passwords and secrets within credential providers.

The CredentialProvider API in Hadoop allows for the separation of applications and how they store their required passwords/secrets. In order to indicate a particular provider type and location, the user must provide the hadoop.security.credential.provider.path configuration element in core-site.xml or use the command line option -provider on each of the following commands. This provider path is a comma-separated list of URLs that indicates the type and location of a list of providers that should be consulted. For example, the following path: user:///,jceks://file/tmp/test.jceks,jceks://hdfs@nn1.example.com/my/path/test.jceks

indicates that the current user's credentials file should be consulted through the User Provider, that the local file located at /tmp/test.jceks is a Java Keystore Provider and that the file located within HDFS at nn1.example.com/my/path/test.jceks is also a store for a Java Keystore Provider.

When utilizing the credential command it will often be for provisioning a password or secret to a particular credential store provider. In order to explicitly indicate which provider store to use the -provider option should be used. Otherwise, given a path of multiple providers, the first non-transient provider will be used. This may or may not be the one that you intended.

Example: hadoop credential list -provider jceks://file/tmp/test.jceks

distch

Usage: hadoop distch [-f urilist_url] [-i] [-log logdir] path:owner:group:permissions

COMMAND_OPTION	Description
-f	List of objects to change
-i	Ignore failures
-log	Directory to log output

Change the ownership and permissions on many files at once.

distcp

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

fs

This command is documented in the File System Shell Guide. It is a synonym for hdfs dfs when HDFS is in use.

jar

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

Runs a jar file.

Use yarn jar to launch YARN applications instead.

jnipath

Usage: hadoop jnipath

Print the computed java.library.path.

kerbname

Usage: hadoop kerbname principal

Convert the named principal via the auth_to_local rules to the Hadoop user name.

Example: hadoop kerbname user@EXAMPLE.COM

key

Usage: hadoop key <subcommand> [options]

COMMAND_OPTION	Description
create keyname [-cipher cipher] [-size size] [-description description] [-attr attribute=value] [-provider provider] [-help]	Creates a new key for the name specified by the keyname argument within the provider specified by the -provider argument. You may specify a cipher with the -cipher argument. The default cipher is currently "AES/CTR/NoPadding". The default keysize is 128. You may specify the requested key length using the -size argument. Arbitrary attribute=value style attributes may be specified using the -attr argument. -attr may be specified multiple times, once per attribute.
roll keyname [-provider provider] [-help]	Creates a new version for the specified key within the provider indicated using the -provider argument
delete keyname [-provider provider] [-f] [-help]	Deletes all versions of the key specified by the keyname argument from within the provider specified by -provider. The command asks for user confirmation unless -f is specified.
list [-provider provider] [-metadata] [-help]	Displays the keynames contained within a particular provider as configured in core-site.xml or specified with the -provider argument. -metadata displays the metadata.
-help	Prints usage of this command

Manage keys via the KeyProvider. For details on KeyProviders, see the Transparent Encryption Guide.

NOTE: Some KeyProviders (e.g. org.apache.hadoop.crypto.key.JavaKeyStoreProvider) does not support uppercase key names.

trace

View and modify Hadoop tracing settings. See the Tracing Guide.

version

Usage: hadoop version

Prints the version.

CLASSNAME

Usage: hadoop CLASSNAME

Runs the class named CLASSNAME. The class must be part of a package.

Administration Commands

Commands useful for administrators of a hadoop cluster.

daemonlog

Usage:

hadoop daemonlog -getlevel <host:httpport> <classname>
hadoop daemonlog -setlevel <host:httpport> <classname> <level>

COMMAND_OPTION	Description
-getlevel host:httpport classname	Prints the log level of the log identified by a qualified classname, in the daemon running at host:httpport. This command internally connects to http://<host:httpport>/logLevel?log=<classname>
-setlevel host:httpport classname level	Sets the log level of the log identified by a qualified classname, in the daemon running at host:httpport. This command internally connects to http://<host:httpport>/logLevel?log=<classname>&level=<level>

Get/Set the log level for a Log identified by a qualified class name in the daemon.

Example: $ bin/hadoop daemonlog -setlevel 127.0.0.1:9870 org.apache.hadoop.hdfs.server.namenode.NameNode DEBUG

Files

etc/hadoop/hadoop-env.sh

This file stores the global settings used by all Hadoop shell commands.

etc/hadoop/hadoop-user-functions.sh

This file allows for advanced users to override some shell functionality.

~/.hadooprc

This stores the personal environment for an individual user. It is processed after the hadoop-env.sh and hadoop-user-functions.sh files and can contain the same settings.