Hadoop配置文件hadoop-env.sh

hadoop-env.sh 是 Hadoop 配置中的一个关键脚本，它定义了 Hadoop 运行环境的变量。这个脚本通常位于 Hadoop 安装目录下的 etc/hadoop/ 目录中。在该脚本中，你可以设置各种环境变量来影响 Hadoop 的行为，例如 Java 的路径、Hadoop 的临时目录、以及 JVM 的内存参数等。

下面是一个典型的 hadoop-env.sh 文件的示例内容：

#!/bin/bash

# The java implementation to use.
export JAVA_HOME=/usr/lib/jvm/java-8-openjdk-amd64

# Extra Java CLASSPATH elements.  This is for Hadoop internal use and
# shouldn't normally be modified.
export HADOOP_CLASSPATH=

# Extra Java runtime options.  Empty by default.
export HADOOP_OPTS="-Djava.net.preferIPv4Stack=true"

# Where log files are stored.  $HADOOP_HOME/logs by default.
export HADOOP_LOG_DIR=${HADOOP_HOME}/logs

# A string representing this instance of hadoop. $USER by default.
export HADOOP_IDENT_STRING=$USER

# The scheduling priority for daemon processes.  See 'man nice'.
export HADOOP_NICENESS=10

# The directory where pid files are stored. /tmp by default.
export HADOOP_PID_DIR=/var/run/hadoop

# The directory where temporary files are stored. /tmp by default.
export HADOOP_TMP_DIR=/var/tmp/hadoop-${HADOOP_IDENT_STRING}

# Extra ssh options. Empty by default.
export HADOOP_SSH_OPTS="-o ConnectTimeout=1 -o SendEnv=HADOOP_CONF_DIR"

# The amount of heap to reserve before the GC kicks in (in MB).
# By default, we set it to 85% of physical memory.
# export HADOOP_HEAPSIZE=1024

# The maximum virtual memory a Hadoop child process can consume before
# it is killed.  Specify -1 for unlimited.
# export HADOOP_CHILD_VMEM_LIMIT=-1

# The maximum paged memory a Hadoop child process can consume before
# it is killed.  Specify -1 for unlimited.
# export HADOOP_CHILD_PMEM_LIMIT=-1

你可能需要根据你的系统环境和需求修改这些变量。例如，如果你使用的是不同的 Java 版本，你需要更新 JAVA_HOME 变量以指向正确的 Java 安装路径。同样，HADOOP_OPTS 可以用于调整 JVM 参数，比如增加或减少分配给 Hadoop 进程的堆内存。

请确保在修改后保存文件并重新启动 Hadoop 服务以便让新的设置生效。