一、背景介绍

在单台 CentOS 7.4 系统的服务器上安装 hadoop，用作平时开发代码的测试环境，其中安装包含 hadoop-3.2.2.tar.gz、spark-3.0.1-bin-hadoop3.2.tgz。

二、遇到问题

问题1：进入hadoop目录执行 sbin/start-all.sh 时报错：localhost Permission denied (publickey,gssapi-keyex,gssapi-with-mic,password).

做本机信任

ssh-keygen -t rsa -P '' -f ~/.ssh/id_rsa
cat ~/.ssh/id_rsa.pub  >> ~/.ssh/authorized_keys

问题2：进入hadoop目录执行 sbin/start-all.sh 时报错：ERROR: JAVA_HOME is not set and could not be found.

修改 hadoop/etc/hadoop/hadoop-env.sh 脚本文件内容，可参考：
export JAVA_HOME=/opt/software/jdk/java

三、我的总结

以hadoop安装到 /opt/software/big_data_env 且source_hadoop_env.sh放置于hadoop目录中为例：

1、安装前

• 完成相关依赖安装（java等）、环境设置（本机信任等）
• 完成core-site.xml、hdfs-site.xml、yarn-site.xml、mapred-site.xml等4个配置文件的配置，提前避免一些安装问题
• 编写环境变量加载脚本，如：source_hadoop_env.sh

core-site.xml

<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>
<configuration>
  <property>
     <name>fs.defaultFS</name>
     <value>hdfs://localhost:19000</value>
  </property>
</configuration>

hdfs-site.xml

<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>
<configuration>
  <property>
     <name>dfs.replication</name>
     <value>1</value>
  </property>
  <property>
     <name>dfs.namenode.http-address</name>
     <value>0.0.0.0:19870</value>
     <description>
      The address and the base port where the dfs namenode web ui wiil listen on.
    </description>
  </property>
  <property>
     <name>dfs.datanode.data.dir</name>
     <value>file:///opt/software/dfs/data</value>
  </property>
</configuration>

yarn-site.xml

<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>
<configuration>
  <property>
     <name>yarn.nodemanager.aux-services</name>
     <value>mapreduce_shuffle</value>
  </property>
  <property>
     <name>yarn.nodemanager.resource.detect-hardware-capabilities</name>
     <value>true</value>
  </property>
  <property>
     <name>yarn.nodemanager.resource.memory-mb</name>
     <value>-1</value>
  </property>
  <property>
     <name>yarn.scheduler.maximum-allocation-mb</name>
     <value>2048</value>
  </property>
  <property>
     <name>yarn.nodemanager.resource.cpu-vcores</name>
     <value>-1</value>
  </property>
  <property>
     <name>yarn.nodemanager.env-whitelist</name>
     <value>JAVA_HOME,HADOOP_COMMON_HOME,HADOOP_HDFS_HOME,HADOOP_CONF_DIR,CLASSPATH_PREPEND_DISTCACHE,HADOOP_YARN_HOME,HADOOP_HOME,PATH,LANG,TZ,HADOOP_MAPRED_HOME</value>
  </property>
  <property>
     <name>yarn.nodemanager.disk-health-checker.max-disk-utilization-per-disk-percentage</name>
     <value>98.5</value>
  </property>
  <property>
     <name>yarn.nodemanager.webapp.address</name>
     <value>${yarn.resourcemanager.hostname}:18088</value>
    <description>
      The http address of the RM web application.
      IF onlt a host is provided as the value,
      the webapp will be served on a random port.
    </description>
  </property>
</configuration>

mapred-site.xml

<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>
<configuration>
  <property>
     <name>mapreduce.framework.name</name>
     <value>yarn</value>
  </property>
  <property>
     <name>mapreduce.application.classpath</name>
     <value>$HADOOP_MAPRED_HOME/share/hadoop/mapreduce/*:$HADOOP_MAPRED_HOME/share/hadoop/mapreduce/lib/*</value>
  </property>
</configuration>

source_hadoop_env.sh

#!/usr/bin/bash
export JAVA_HOME=/opt/software/jdk/java
export HADOOP_HOME=/opt/software/big_data_env/hadoop
export PATH=${JAVA_HOME}/bin:${HADOOP_HOME}:${HADOOP_HOME}/bin:$PATH

export HDFS_NAMENODE_USER="root"
export HDFS_DATANODE_USER="root"
export HDFS_SECONDARYNAMENODE_USER="root"
export YARN_RESOURCEMANAGER_USER="root"
export YARN_NODEMANAGER_USER="root"

export HADOOP_CONF_DIR=/opt/software/big_data_env/hadoop/etc/hadoop

2、安装中

• 执行 sbin/start-all.sh 前，加载环境变量（使用自动加载方法）并格式化namenode

sed -i '$a\source /opt/software/big_data_env/hadoop/source_hadoop_env.sh' ~/.bash_profile
source ~/.bash_profile
hadoop namenode -format
sbin/start-all.sh

3、安装后

• 查看进程是否存在（包含NameNode、DataNode、ResourceManager、SecondaryNameNode、NodeManager）
  jps
• 查看 /opt/software/hadoop/logs 中各个日志打印内容是否有报错，其中如：
  tail -5000f /opt/software/big_data_env/hadoop/logs/hadoop-root-datanode-*.log
• 查看页面是否可以正常访问
  1）hdfs namenode web interface：htttp://{主机地址}:19870
  2）hdfs file system: htttp://{主机地址}:19870/explorer.html
  3）yarn resourcemanager web interface: htttp://{主机地址}:18088/cluster/scheduler
  备注：从3.0开始 hdfs file system 可以直接上传下载数据文件.