hadoop-common-project/hadoop-common/src/main/conf/hadoop-env.sh - hadoop-common - Git at Google

 #
 # Licensed to the Apache Software Foundation (ASF) under one
 # or more contributor license agreements.  See the NOTICE file
 # distributed with this work for additional information
 # regarding copyright ownership.  The ASF licenses this file
 # to you under the Apache License, Version 2.0 (the
 # "License"); you may not use this file except in compliance
 # with the License.  You may obtain a copy of the License at
 #
 #     http://www.apache.org/licenses/LICENSE-2.0
 #
 # Unless required by applicable law or agreed to in writing, software
 # distributed under the License is distributed on an "AS IS" BASIS,
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.

 # Set Hadoop-specific environment variables here.

 ##
 ## THIS FILE ACTS AS THE MASTER FILE FOR ALL HADOOP PROJECTS.
 ## SETTINGS HERE WILL BE READ BY ALL HADOOP COMMANDS.  THEREFORE,
 ## ONE CAN USE THIS FILE TO SET YARN, HDFS, AND MAPREDUCE
 ## CONFIGURATION OPTIONS INSTEAD OF xxx-env.sh.
 ##
 ## Precedence rules:
 ##
 ## {yarn-env.sh|hdfs-env.sh} > hadoop-env.sh > hard-coded defaults
 ##
 ## {YARN_xyz|HDFS_xyz} > HADOOP_xyz > hard-coded defaults
 ##

 # Many of the options here are built from the perspective that users
 # may want to provide OVERWRITING values on the command line.
 # For example:
 #
 #  JAVA_HOME=/usr/java/testing hdfs dfs -ls
 #
 # Therefore, the vast majority (BUT NOT ALL!) of these defaults
 # are configured for substitution and not append.  If you would
 # like append, you'll # need to modify this file accordingly.

 ###
 # Generic settings for HADOOP
 ###

 # Technically, the only required environment variable is JAVA_HOME.
 # All others are optional.  However, our defaults are probably not
 # your defaults.  Many sites configure these options outside of Hadoop,
 # such as in /etc/profile.d

 # The java implementation to use.
 export JAVA_HOME=${JAVA_HOME:-"hadoop-env.sh is not configured"}

 # Location of Hadoop's configuration information.  i.e., where this
 # file is probably living.  You will almost certainly want to set
 # this in /etc/profile.d or equivalent.
 # export HADOOP_CONF_DIR=$HADOOP_PREFIX/etc/hadoop

 # The maximum amount of heap to use, in MB. Default is 1024.
 # export HADOOP_HEAPSIZE=1024

 # Extra Java runtime options for all Hadoop commands. We don't support
 # IPv6 yet/still, so by default we set preference to IPv4.
 # export HADOOP_OPTS="-Djava.net.preferIPv4Stack=true"

 # Some parts of the shell code may do special things dependent upon
 # the operating system.  We have to set this here. See the next
 # section as to why....
 export HADOOP_OS_TYPE=${HADOOP_OS_TYPE:-$(uname -s)}


 # Under certain conditions, Java on OS X will throw SCDynamicStore errors
 # in the system logs.
 # See HADOOP-8719 for more information.  If you need Kerberos
 # support on OS X, you'll want to change/remove this extra bit.
 case ${HADOOP_OS_TYPE} in
   Darwin*)
     export HADOOP_OPTS="${HADOOP_OPTS} -Djava.security.krb5.realm= "
     export HADOOP_OPTS="${HADOOP_OPTS} -Djava.security.krb5.kdc= "
     export HADOOP_OPTS="${HADOOP_OPTS} -Djava.security.krb5.conf= "
   ;;
 esac

 # Extra Java runtime options for Hadoop clients (i.e., hdfs dfs -blah)
 # These get added to HADOOP_OPTS for such commands.  In most cases,
 # this should be left empty and let users supply it on the
 # command line.
 # extra HADOOP_CLIENT_OPTS=""

 #
 # A note about classpaths.
 #
 # The classpath is configured such that entries are stripped prior
 # to handing to Java based either upon duplication or non-existence.
 # Wildcards and/or directories are *NOT* expanded as the
 # de-duplication is fairly simple.  So if two directories are in
 # the classpath that both contain awesome-methods-1.0.jar,
 # awesome-methods-1.0.jar will still be seen by java.  But if
 # the classpath specifically has awesome-methods-1.0.jar from the
 # same directory listed twice, the last one will be removed.
 #

 # An additional, custom CLASSPATH.  This is really meant for
 # end users, but as an administrator, one might want to push
 # something extra in here too, such as the jar to the topology
 # method.  Just be sure to append to the existing HADOOP_USER_CLASSPATH
 # so end users have a way to add stuff.
 # export HADOOP_USER_CLASSPATH="/some/cool/path/on/your/machine"

 # Should HADOOP_USER_CLASSPATH be first in the official CLASSPATH?
 # export HADOOP_USER_CLASSPATH_FIRST="yes"

 # If HADOOP_USE_CLIENT_CLASSLOADER is set, HADOOP_CLASSPATH along with the main
 # jar are handled by a separate isolated client classloader. If it is set,
 # HADOOP_USER_CLASSPATH_FIRST is ignored. Can be defined by doing
 # export HADOOP_USE_CLIENT_CLASSLOADER=true

 # HADOOP_CLIENT_CLASSLOADER_SYSTEM_CLASSES overrides the default definition of
 # system classes for the client classloader when HADOOP_USE_CLIENT_CLASSLOADER
 # is enabled. Names ending in '.' (period) are treated as package names, and
 # names starting with a '-' are treated as negative matches. For example,
 # export HADOOP_CLIENT_CLASSLOADER_SYSTEM_CLASSES="-org.apache.hadoop.UserClass,java.,javax.,org.apache.hadoop."

 ###
 # Options for remote shell connectivity
 ###

 # There are some optional components of hadoop that allow for
 # command and control of remote hosts.  For example,
 # start-dfs.sh will attempt to bring up all NNs, DNS, etc.

 # Options to pass to SSH when one of the "log into a host and
 # start/stop daemons" scripts is executed
 # export HADOOP_SSH_OPTS="-o BatchMode=yes -o StrictHostKeyChecking=no -o ConnectTimeout=10s"

 # The built-in ssh handler will limit itself to 10 simultaneous connections.
 # For pdsh users, this sets the fanout size ( -f )
 # Change this to increase/decrease as necessary.
 # export HADOOP_SSH_PARALLEL=10

 # Filename which contains all of the hosts for any remote execution
 # helper scripts # such as slaves.sh, start-dfs.sh, etc.
 # export HADOOP_SLAVES="${HADOOP_CONF_DIR}/slaves"

 ###
 # Options for all daemons
 ###
 #

 #
 # You can define variables right here and then re-use them later on.
 # For example, it is common to use the same garbage collection settings
 # for all the daemons.  So we could define:
 #
 # export HADOOP_GC_SETTINGS="-verbose:gc -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps"
 #
 # .. and then use it as per the b option under the namenode.

 # Where (primarily) daemon log files are stored.
 # $HADOOP_PREFIX/logs by default.
 # export HADOOP_LOG_DIR=${HADOOP_PREFIX}/logs

 # A string representing this instance of hadoop. $USER by default.
 # This is used in writing log and pid files, so keep that in mind!
 # export HADOOP_IDENT_STRING=$USER

 # How many seconds to pause after stopping a daemon
 # export HADOOP_STOP_TIMEOUT=5

 # Where pid files are stored.  /tmp by default.
 # export HADOOP_PID_DIR=/tmp

 # Default log level and output location
 # This sets the hadoop.root.logger property
 # export HADOOP_ROOT_LOGGER=INFO,console

 # Default log level for daemons spawned explicitly by hadoop-daemon.sh
 # This sets the hadoop.root.logger property
 # export HADOOP_DAEMON_ROOT_LOGGER=INFO,RFA

 # Default log level and output location for security-related messages.
 # It sets -Dhadoop.security.logger on the command line.
 # You will almost certainly want to change this on a per-daemon basis!
 # export HADOOP_SECURITY_LOGGER=INFO,NullAppender

 # Default log level for file system audit messages.
 # It sets -Dhdfs.audit.logger on the command line.
 # You will almost certainly want to change this on a per-daemon basis!
 # export HADOOP_AUDIT_LOGGER=INFO,NullAppender

 # Default process priority level
 # Note that sub-processes will also run at this level!
 # export HADOOP_NICENESS=0

 # Default name for the service level authorization file
 # export HADOOP_POLICYFILE="hadoop-policy.xml"

 ###
 # Secure/privileged execution
 ###

 #
 # Out of the box, Hadoop uses jsvc from Apache Commons to launch daemons
 # on privileged ports.  This functionality can be replaced by providing
 # custom functions.  See hadoop-functions.sh for more information.
 #

 # The jsvc implementation to use. Jsvc is required to run secure datanodes.
 # export JSVC_HOME=/usr/bin

 #
 # This directory contains pids for secure and privileged processes.
 #export HADOOP_SECURE_PID_DIR=${HADOOP_PID_DIR}

 #
 # This directory contains the logs for secure and privileged processes.
 # export HADOOP_SECURE_LOG=${HADOOP_LOG_DIR}

 #
 # When running a secure daemon, the default value of HADOOP_IDENT_STRING
 # ends up being a bit bogus.  Therefore, by default, the code will
 # replace HADOOP_IDENT_STRING with HADOOP_SECURE_xx_USER.  If you want
 # to keep HADOOP_IDENT_STRING untouched, then uncomment this line.
 # export HADOOP_SECURE_IDENT_PRESERVE="true"

 ###
 # NameNode specific parameters
 ###
 # Specify the JVM options to be used when starting the NameNode.
 # These options will be appended to the options specified as HADOOP_OPTS
 # and therefore may override any similar flags set in HADOOP_OPTS
 #
 # a) Set JMX options
 # export HADOOP_NAMENODE_OPTS="-Dcom.sun.management.jmxremote=true -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false -Dcom.sun.management.jmxremote.port=1026"
 #
 # b) Set garbage collection logs
 # export HADOOP_NAMENODE_OPTS="${HADOOP_GC_SETTINGS} -Xloggc:${HADOOP_LOG_DIR}/gc-rm.log-$(date +'%Y%m%d%H%M')"
 #
 # c) ... or set them directly
 # export HADOOP_NAMENODE_OPTS="-verbose:gc -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps -Xloggc:${HADOOP_LOG_DIR}/gc-rm.log-$(date +'%Y%m%d%H%M')"

 # this is the default:
 # export HADOOP_NAMENODE_OPTS="-Dhadoop.security.logger=INFO,RFAS -Dhdfs.audit.logger=INFO,NullAppender"

 ###
 # SecondaryNameNode specific parameters
 ###
 # Specify the JVM options to be used when starting the SecondaryNameNode.
 # These options will be appended to the options specified as HADOOP_OPTS
 # and therefore may override any similar flags set in HADOOP_OPTS
 #
 # This is the default:
 # export HADOOP_SECONDARYNAMENODE_OPTS="-Dhadoop.security.logger=INFO,RFAS -Dhdfs.audit.logger=INFO,NullAppender"

 ###
 # DataNode specific parameters
 ###
 # Specify the JVM options to be used when starting the DataNode.
 # These options will be appended to the options specified as HADOOP_OPTS
 # and therefore may override any similar flags set in HADOOP_OPTS
 #
 # This is the default:
 # export HADOOP_DATANODE_OPTS="-Dhadoop.security.logger=ERROR,RFAS"

 # On secure datanodes, user to run the datanode as after dropping privileges
 # This **MUST** be uncommented to enable secure HDFS!
 # export HADOOP_SECURE_DN_USER=hdfs

 # Supplemental options for secure datanodes
 # By default, we use jsvc which needs to know to launch a
 # server jvm.
 # export HADOOP_DN_SECURE_EXTRA_OPTS="-jvm server"

 # Where datanode log files are stored in the secure data environment.
 # export HADOOP_SECURE_DN_LOG_DIR=${HADOOP_SECURE_LOG_DIR}

 # Where datanode pid files are stored in the secure data environment.
 # export HADOOP_SECURE_DN_PID_DIR=${HADOOP_SECURE_PID_DIR}

 ###
 # NFS3 Gateway specific parameters
 ###
 # Specify the JVM options to be used when starting the NFS3 Gateway.
 # These options will be appended to the options specified as HADOOP_OPTS
 # and therefore may override any similar flags set in HADOOP_OPTS
 #
 # export HADOOP_NFS3_OPTS=""

 # Specify the JVM options to be used when starting the Hadoop portmapper.
 # These options will be appended to the options specified as HADOOP_OPTS
 # and therefore may override any similar flags set in HADOOP_OPTS
 #
 # export HADOOP_PORTMAP_OPTS="-Xmx512m"

 # Supplemental options for priviliged gateways
 # By default, we use jsvc which needs to know to launch a
 # server jvm.
 # export HADOOP_NFS3_SECURE_EXTRA_OPTS="-jvm server"

 # On privileged gateways, user to run the gateway as after dropping privileges
 # export HADOOP_PRIVILEGED_NFS_USER=nfsserver

 ###
 # ZKFailoverController specific parameters
 ###
 # Specify the JVM options to be used when starting the ZKFailoverController.
 # These options will be appended to the options specified as HADOOP_OPTS
 # and therefore may override any similar flags set in HADOOP_OPTS
 #
 # export HADOOP_ZKFC_OPTS=""

 ###
 # QuorumJournalNode specific parameters
 ###
 # Specify the JVM options to be used when starting the QuorumJournalNode.
 # These options will be appended to the options specified as HADOOP_OPTS
 # and therefore may override any similar flags set in HADOOP_OPTS
 #
 # export HADOOP_JOURNALNODE_OPTS=""

 ###
 # HDFS Balancer specific parameters
 ###
 # Specify the JVM options to be used when starting the HDFS Balancer.
 # These options will be appended to the options specified as HADOOP_OPTS
 # and therefore may override any similar flags set in HADOOP_OPTS
 #
 # export HADOOP_BALANCER_OPTS=""

 ###
 # Advanced Users Only!
 ###

 #
 # When building Hadoop, you can add the class paths to your commands
 # via this special env var:
 # HADOOP_ENABLE_BUILD_PATHS="true"

 # You can do things like replace parts of the shell underbelly.
 # Most of this code is in hadoop-functions.sh.
 #
 #
 # For example, if you want to add compression to the rotation
 # menthod for the .out files that daemons generate, you can do
 # that by redefining the hadoop_rotate_log function by
 # uncommenting this code block:

 #function hadoop_rotate_log
 #{
 #  #
 #  # log rotation (mainly used for .out files)
 #  # Users are likely to replace this one for something
 #  # that gzips or uses dates or who knows what.
 #  #
 #  # be aware that &1 and &2 might go through here
 #  # so don't do anything too crazy...
 #  #
 #  local log=$1;
 #  local num=${2:-5};
 #
 #  if [[ -f "${log}" ]]; then # rotate logs
 #    while [[ ${num} -gt 1 ]]; do
 #      #shellcheck disable=SC2086
 #      let prev=${num}-1
 #      if [[ -f "${log}.${prev}" ]]; then
 #        mv "${log}.${prev}" "${log}.${num}"
 #      fi
 #      num=${prev}
 #    done
 #    mv "${log}" "${log}.${num}"
 #    gzip -9 "${log}.${num}"
 #  fi
 #}
 #
 #
 # Another example:  finding java
 #
 # By default, Hadoop assumes that $JAVA_HOME is always defined
 # outside of its configuration. Eons ago, Apple standardized
 # on a helper program called java_home to find it for you.
 #
 #function hadoop_java_setup
 #{
 #
 #  if [[ -z "${JAVA_HOME}" ]]; then
 #     case $HADOOP_OS_TYPE in
 #       Darwin*)
 #          JAVA_HOME=$(/usr/libexec/java_home)
 #          ;;
 #     esac
 #  fi
 #
 #  # Bail if we did not detect it
 #  if [[ -z "${JAVA_HOME}" ]]; then
 #    echo "ERROR: JAVA_HOME is not set and could not be found." 1>&2
 #    exit 1
 #  fi
 #
 #  if [[ ! -d "${JAVA_HOME}" ]]; then
 #     echo "ERROR: JAVA_HOME (${JAVA_HOME}) does not exist." 1>&2
 #     exit 1
 #  fi
 #
 #  JAVA="${JAVA_HOME}/bin/java"
 #
 #  if [[ ! -x ${JAVA} ]]; then
 #    echo "ERROR: ${JAVA} is not executable." 1>&2
 #    exit 1
 #  fi
 #  JAVA_HEAP_MAX=-Xmx1g
 #  HADOOP_HEAPSIZE=${HADOOP_HEAPSIZE:-128}
 #
 #  # check envvars which might override default args
 #  if [[ -n "$HADOOP_HEAPSIZE" ]]; then
 #    JAVA_HEAP_MAX="-Xmx${HADOOP_HEAPSIZE}m"
 #  fi
 #}
	#
	# Licensed to the Apache Software Foundation (ASF) under one
	# or more contributor license agreements. See the NOTICE file
	# distributed with this work for additional information
	# regarding copyright ownership. The ASF licenses this file
	# to you under the Apache License, Version 2.0 (the
	# "License"); you may not use this file except in compliance
	# with the License. You may obtain a copy of the License at
	#
	# http://www.apache.org/licenses/LICENSE-2.0
	#
	# Unless required by applicable law or agreed to in writing, software
	# distributed under the License is distributed on an "AS IS" BASIS,
	# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	# See the License for the specific language governing permissions and
	# limitations under the License.

	# Set Hadoop-specific environment variables here.

	##
	## THIS FILE ACTS AS THE MASTER FILE FOR ALL HADOOP PROJECTS.
	## SETTINGS HERE WILL BE READ BY ALL HADOOP COMMANDS. THEREFORE,
	## ONE CAN USE THIS FILE TO SET YARN, HDFS, AND MAPREDUCE
	## CONFIGURATION OPTIONS INSTEAD OF xxx-env.sh.
	##
	## Precedence rules:
	##
	## {yarn-env.sh\|hdfs-env.sh} > hadoop-env.sh > hard-coded defaults
	##
	## {YARN_xyz\|HDFS_xyz} > HADOOP_xyz > hard-coded defaults
	##

	# Many of the options here are built from the perspective that users
	# may want to provide OVERWRITING values on the command line.
	# For example:
	#
	# JAVA_HOME=/usr/java/testing hdfs dfs -ls
	#
	# Therefore, the vast majority (BUT NOT ALL!) of these defaults
	# are configured for substitution and not append. If you would
	# like append, you'll # need to modify this file accordingly.

	###
	# Generic settings for HADOOP
	###

	# Technically, the only required environment variable is JAVA_HOME.
	# All others are optional. However, our defaults are probably not
	# your defaults. Many sites configure these options outside of Hadoop,
	# such as in /etc/profile.d

	# The java implementation to use.
	export JAVA_HOME=${JAVA_HOME:-"hadoop-env.sh is not configured"}

	# Location of Hadoop's configuration information. i.e., where this
	# file is probably living. You will almost certainly want to set
	# this in /etc/profile.d or equivalent.
	# export HADOOP_CONF_DIR=$HADOOP_PREFIX/etc/hadoop

	# The maximum amount of heap to use, in MB. Default is 1024.
	# export HADOOP_HEAPSIZE=1024

	# Extra Java runtime options for all Hadoop commands. We don't support
	# IPv6 yet/still, so by default we set preference to IPv4.
	# export HADOOP_OPTS="-Djava.net.preferIPv4Stack=true"

	# Some parts of the shell code may do special things dependent upon
	# the operating system. We have to set this here. See the next
	# section as to why....
	export HADOOP_OS_TYPE=${HADOOP_OS_TYPE:-$(uname -s)}


	# Under certain conditions, Java on OS X will throw SCDynamicStore errors
	# in the system logs.
	# See HADOOP-8719 for more information. If you need Kerberos
	# support on OS X, you'll want to change/remove this extra bit.
	case ${HADOOP_OS_TYPE} in
	Darwin*)
	export HADOOP_OPTS="${HADOOP_OPTS} -Djava.security.krb5.realm= "
	export HADOOP_OPTS="${HADOOP_OPTS} -Djava.security.krb5.kdc= "
	export HADOOP_OPTS="${HADOOP_OPTS} -Djava.security.krb5.conf= "
	;;
	esac

	# Extra Java runtime options for Hadoop clients (i.e., hdfs dfs -blah)
	# These get added to HADOOP_OPTS for such commands. In most cases,
	# this should be left empty and let users supply it on the
	# command line.
	# extra HADOOP_CLIENT_OPTS=""

	#
	# A note about classpaths.
	#
	# The classpath is configured such that entries are stripped prior
	# to handing to Java based either upon duplication or non-existence.
	# Wildcards and/or directories are NOT expanded as the
	# de-duplication is fairly simple. So if two directories are in
	# the classpath that both contain awesome-methods-1.0.jar,
	# awesome-methods-1.0.jar will still be seen by java. But if
	# the classpath specifically has awesome-methods-1.0.jar from the
	# same directory listed twice, the last one will be removed.
	#

	# An additional, custom CLASSPATH. This is really meant for
	# end users, but as an administrator, one might want to push
	# something extra in here too, such as the jar to the topology
	# method. Just be sure to append to the existing HADOOP_USER_CLASSPATH
	# so end users have a way to add stuff.
	# export HADOOP_USER_CLASSPATH="/some/cool/path/on/your/machine"

	# Should HADOOP_USER_CLASSPATH be first in the official CLASSPATH?
	# export HADOOP_USER_CLASSPATH_FIRST="yes"

	# If HADOOP_USE_CLIENT_CLASSLOADER is set, HADOOP_CLASSPATH along with the main
	# jar are handled by a separate isolated client classloader. If it is set,
	# HADOOP_USER_CLASSPATH_FIRST is ignored. Can be defined by doing
	# export HADOOP_USE_CLIENT_CLASSLOADER=true

	# HADOOP_CLIENT_CLASSLOADER_SYSTEM_CLASSES overrides the default definition of
	# system classes for the client classloader when HADOOP_USE_CLIENT_CLASSLOADER
	# is enabled. Names ending in '.' (period) are treated as package names, and
	# names starting with a '-' are treated as negative matches. For example,
	# export HADOOP_CLIENT_CLASSLOADER_SYSTEM_CLASSES="-org.apache.hadoop.UserClass,java.,javax.,org.apache.hadoop."

	###
	# Options for remote shell connectivity
	###

	# There are some optional components of hadoop that allow for
	# command and control of remote hosts. For example,
	# start-dfs.sh will attempt to bring up all NNs, DNS, etc.

	# Options to pass to SSH when one of the "log into a host and
	# start/stop daemons" scripts is executed
	# export HADOOP_SSH_OPTS="-o BatchMode=yes -o StrictHostKeyChecking=no -o ConnectTimeout=10s"

	# The built-in ssh handler will limit itself to 10 simultaneous connections.
	# For pdsh users, this sets the fanout size ( -f )
	# Change this to increase/decrease as necessary.
	# export HADOOP_SSH_PARALLEL=10

	# Filename which contains all of the hosts for any remote execution
	# helper scripts # such as slaves.sh, start-dfs.sh, etc.
	# export HADOOP_SLAVES="${HADOOP_CONF_DIR}/slaves"

	###
	# Options for all daemons
	###
	#

	#
	# You can define variables right here and then re-use them later on.
	# For example, it is common to use the same garbage collection settings
	# for all the daemons. So we could define:
	#
	# export HADOOP_GC_SETTINGS="-verbose:gc -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps"
	#
	# .. and then use it as per the b option under the namenode.

	# Where (primarily) daemon log files are stored.
	# $HADOOP_PREFIX/logs by default.
	# export HADOOP_LOG_DIR=${HADOOP_PREFIX}/logs

	# A string representing this instance of hadoop. $USER by default.
	# This is used in writing log and pid files, so keep that in mind!
	# export HADOOP_IDENT_STRING=$USER

	# How many seconds to pause after stopping a daemon
	# export HADOOP_STOP_TIMEOUT=5

	# Where pid files are stored. /tmp by default.
	# export HADOOP_PID_DIR=/tmp

	# Default log level and output location
	# This sets the hadoop.root.logger property
	# export HADOOP_ROOT_LOGGER=INFO,console

	# Default log level for daemons spawned explicitly by hadoop-daemon.sh
	# This sets the hadoop.root.logger property
	# export HADOOP_DAEMON_ROOT_LOGGER=INFO,RFA

	# Default log level and output location for security-related messages.
	# It sets -Dhadoop.security.logger on the command line.
	# You will almost certainly want to change this on a per-daemon basis!
	# export HADOOP_SECURITY_LOGGER=INFO,NullAppender

	# Default log level for file system audit messages.
	# It sets -Dhdfs.audit.logger on the command line.
	# You will almost certainly want to change this on a per-daemon basis!
	# export HADOOP_AUDIT_LOGGER=INFO,NullAppender

	# Default process priority level
	# Note that sub-processes will also run at this level!
	# export HADOOP_NICENESS=0

	# Default name for the service level authorization file
	# export HADOOP_POLICYFILE="hadoop-policy.xml"

	###
	# Secure/privileged execution
	###

	#
	# Out of the box, Hadoop uses jsvc from Apache Commons to launch daemons
	# on privileged ports. This functionality can be replaced by providing
	# custom functions. See hadoop-functions.sh for more information.
	#

	# The jsvc implementation to use. Jsvc is required to run secure datanodes.
	# export JSVC_HOME=/usr/bin

	#
	# This directory contains pids for secure and privileged processes.
	#export HADOOP_SECURE_PID_DIR=${HADOOP_PID_DIR}

	#
	# This directory contains the logs for secure and privileged processes.
	# export HADOOP_SECURE_LOG=${HADOOP_LOG_DIR}

	#
	# When running a secure daemon, the default value of HADOOP_IDENT_STRING
	# ends up being a bit bogus. Therefore, by default, the code will
	# replace HADOOP_IDENT_STRING with HADOOP_SECURE_xx_USER. If you want
	# to keep HADOOP_IDENT_STRING untouched, then uncomment this line.
	# export HADOOP_SECURE_IDENT_PRESERVE="true"

	###
	# NameNode specific parameters
	###
	# Specify the JVM options to be used when starting the NameNode.
	# These options will be appended to the options specified as HADOOP_OPTS
	# and therefore may override any similar flags set in HADOOP_OPTS
	#
	# a) Set JMX options
	# export HADOOP_NAMENODE_OPTS="-Dcom.sun.management.jmxremote=true -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false -Dcom.sun.management.jmxremote.port=1026"
	#
	# b) Set garbage collection logs
	# export HADOOP_NAMENODE_OPTS="${HADOOP_GC_SETTINGS} -Xloggc:${HADOOP_LOG_DIR}/gc-rm.log-$(date +'%Y%m%d%H%M')"
	#
	# c) ... or set them directly
	# export HADOOP_NAMENODE_OPTS="-verbose:gc -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps -Xloggc:${HADOOP_LOG_DIR}/gc-rm.log-$(date +'%Y%m%d%H%M')"

	# this is the default:
	# export HADOOP_NAMENODE_OPTS="-Dhadoop.security.logger=INFO,RFAS -Dhdfs.audit.logger=INFO,NullAppender"

	###
	# SecondaryNameNode specific parameters
	###
	# Specify the JVM options to be used when starting the SecondaryNameNode.
	# These options will be appended to the options specified as HADOOP_OPTS
	# and therefore may override any similar flags set in HADOOP_OPTS
	#
	# This is the default:
	# export HADOOP_SECONDARYNAMENODE_OPTS="-Dhadoop.security.logger=INFO,RFAS -Dhdfs.audit.logger=INFO,NullAppender"

	###
	# DataNode specific parameters
	###
	# Specify the JVM options to be used when starting the DataNode.
	# These options will be appended to the options specified as HADOOP_OPTS
	# and therefore may override any similar flags set in HADOOP_OPTS
	#
	# This is the default:
	# export HADOOP_DATANODE_OPTS="-Dhadoop.security.logger=ERROR,RFAS"

	# On secure datanodes, user to run the datanode as after dropping privileges
	# This MUST be uncommented to enable secure HDFS!
	# export HADOOP_SECURE_DN_USER=hdfs

	# Supplemental options for secure datanodes
	# By default, we use jsvc which needs to know to launch a
	# server jvm.
	# export HADOOP_DN_SECURE_EXTRA_OPTS="-jvm server"

	# Where datanode log files are stored in the secure data environment.
	# export HADOOP_SECURE_DN_LOG_DIR=${HADOOP_SECURE_LOG_DIR}

	# Where datanode pid files are stored in the secure data environment.
	# export HADOOP_SECURE_DN_PID_DIR=${HADOOP_SECURE_PID_DIR}

	###
	# NFS3 Gateway specific parameters
	###
	# Specify the JVM options to be used when starting the NFS3 Gateway.
	# These options will be appended to the options specified as HADOOP_OPTS
	# and therefore may override any similar flags set in HADOOP_OPTS
	#
	# export HADOOP_NFS3_OPTS=""

	# Specify the JVM options to be used when starting the Hadoop portmapper.
	# These options will be appended to the options specified as HADOOP_OPTS
	# and therefore may override any similar flags set in HADOOP_OPTS
	#
	# export HADOOP_PORTMAP_OPTS="-Xmx512m"

	# Supplemental options for priviliged gateways
	# By default, we use jsvc which needs to know to launch a
	# server jvm.
	# export HADOOP_NFS3_SECURE_EXTRA_OPTS="-jvm server"

	# On privileged gateways, user to run the gateway as after dropping privileges
	# export HADOOP_PRIVILEGED_NFS_USER=nfsserver

	###
	# ZKFailoverController specific parameters
	###
	# Specify the JVM options to be used when starting the ZKFailoverController.
	# These options will be appended to the options specified as HADOOP_OPTS
	# and therefore may override any similar flags set in HADOOP_OPTS
	#
	# export HADOOP_ZKFC_OPTS=""

	###
	# QuorumJournalNode specific parameters
	###
	# Specify the JVM options to be used when starting the QuorumJournalNode.
	# These options will be appended to the options specified as HADOOP_OPTS
	# and therefore may override any similar flags set in HADOOP_OPTS
	#
	# export HADOOP_JOURNALNODE_OPTS=""

	###
	# HDFS Balancer specific parameters
	###
	# Specify the JVM options to be used when starting the HDFS Balancer.
	# These options will be appended to the options specified as HADOOP_OPTS
	# and therefore may override any similar flags set in HADOOP_OPTS
	#
	# export HADOOP_BALANCER_OPTS=""

	###
	# Advanced Users Only!
	###

	#
	# When building Hadoop, you can add the class paths to your commands
	# via this special env var:
	# HADOOP_ENABLE_BUILD_PATHS="true"

	# You can do things like replace parts of the shell underbelly.
	# Most of this code is in hadoop-functions.sh.
	#
	#
	# For example, if you want to add compression to the rotation
	# menthod for the .out files that daemons generate, you can do
	# that by redefining the hadoop_rotate_log function by
	# uncommenting this code block:

	#function hadoop_rotate_log
	#{
	# #
	# # log rotation (mainly used for .out files)
	# # Users are likely to replace this one for something
	# # that gzips or uses dates or who knows what.
	# #
	# # be aware that &1 and &2 might go through here
	# # so don't do anything too crazy...
	# #
	# local log=$1;
	# local num=${2:-5};
	#
	# if [[ -f "${log}" ]]; then # rotate logs
	# while [[ ${num} -gt 1 ]]; do
	# #shellcheck disable=SC2086
	# let prev=${num}-1
	# if [[ -f "${log}.${prev}" ]]; then
	# mv "${log}.${prev}" "${log}.${num}"
	# fi
	# num=${prev}
	# done
	# mv "${log}" "${log}.${num}"
	# gzip -9 "${log}.${num}"
	# fi
	#}
	#
	#
	# Another example: finding java
	#
	# By default, Hadoop assumes that $JAVA_HOME is always defined
	# outside of its configuration. Eons ago, Apple standardized
	# on a helper program called java_home to find it for you.
	#
	#function hadoop_java_setup
	#{
	#
	# if [[ -z "${JAVA_HOME}" ]]; then
	# case $HADOOP_OS_TYPE in
	# Darwin*)
	# JAVA_HOME=$(/usr/libexec/java_home)
	# ;;
	# esac
	# fi
	#
	# # Bail if we did not detect it
	# if [[ -z "${JAVA_HOME}" ]]; then
	# echo "ERROR: JAVA_HOME is not set and could not be found." 1>&2
	# exit 1
	# fi
	#
	# if [[ ! -d "${JAVA_HOME}" ]]; then
	# echo "ERROR: JAVA_HOME (${JAVA_HOME}) does not exist." 1>&2
	# exit 1
	# fi
	#
	# JAVA="${JAVA_HOME}/bin/java"
	#
	# if [[ ! -x ${JAVA} ]]; then
	# echo "ERROR: ${JAVA} is not executable." 1>&2
	# exit 1
	# fi
	# JAVA_HEAP_MAX=-Xmx1g
	# HADOOP_HEAPSIZE=${HADOOP_HEAPSIZE:-128}
	#
	# # check envvars which might override default args
	# if [[ -n "$HADOOP_HEAPSIZE" ]]; then
	# JAVA_HEAP_MAX="-Xmx${HADOOP_HEAPSIZE}m"
	# fi
	#}