错误:
Error: Could not find or load main class org.apache.hadoop.mapreduce.v2.app.
说明:计算wordcount出错,错误提示补充mapred-site.xml配置
解决方法:1:
这个在我这里不管用(很多博客都说改这个)
在 mapred-site-xml中插入以下代码
<property>
<name>yarn.app.mapreduce.am.env</name>
<value>HADOOP_MAPRED_HOME=${HADOOP_HOME}</value>
</property>
<property>
<name>mapreduce.map.env</name>
<value>HADOOP_MAPRED_HOME=${HADOOP_HOME}</value>
</property>
<property>
<name>mapreduce.reduce.env</name>
<value>HADOOP_MAPRED_HOME=${HADOOP_HOME}</value>
</property>
解决方法2:(亲测有效)
- 1:输入命令:hadoop classpath
举例:
- 2:复制该返回值,并修改成以下格式
<property>
<name>yarn.application.classpath</name>
<value>
/opt/module/hadoop-3.1.3/etc/hadoop,
/opt/module/hadoop-3.1.3/share/hadoop/common/lib/*,
/opt/module/hadoop-3.1.3/share/hadoop/common/*,
/opt/module/hadoop-3.1.3/share/hadoop/hdfs,
/opt/module/hadoop-3.1.3/share/hadoop/hdfs/lib/*,
/opt/module/hadoop-3.1.3/share/hadoop/hdfs/*,
/opt/module/hadoop-3.1.3/share/hadoop/mapreduce/lib/*,
/opt/module/hadoop-3.1.3/share/hadoop/mapreduce/*,
/opt/module/hadoop-3.1.3/share/hadoop/yarn,
/opt/module/hadoop-3.1.3/share/hadoop/yarn/lib/*,
/opt/module/hadoop-3.1.3/share/hadoop/yarn/*,
</value>
</property>
- 3:然后把该代码分别加入到yarn-site.xml,mapred-site.xml里面
举例yarn-site.xml,mapred-site.xml同
!!!!记得将这两个修改的文件分发到其他的机器,然后重启yarn,dfs
成功!!!(开心)
HDFS上结果!!!