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1. Hadoop namenode –format 出现问题
Hadoop namenode –format后,出现错误:未知的名称或服务
解决办法:
sudo vi /etc/hosts
修改 为 127.0.0.1 localhost 你的主机名
我的主机名是hh,就在127.0.0.1的那行后面再加一个hh
2. 执行mapreduce程序出现的错误
[2019-02-03 11:55:40.144]Container exited with a non-zero exit code 1. Error file: prelaunch.err. Last 4096 bytes of prelaunch.err : Last 4096 bytes of stderr : 错误: 找不到或无法加载主类 org.apache.hadoop.mapreduce.v2.app.MRAppMaster
解决办法:
编辑 Hadoop 安装目录下 etc/hadoop/mapred-site.xml 文件，在 标签和 标签之间添加如下配置：
<property>
<name>mapreduce.application.classpath</name>
<value>/opt/module/hadoop-3.2.0/share/hadoop/mapreduce/*,
/opt/module/hadoop-3.2.0/share/hadoop/mapreduce/lib/*</value>
</property>
其中/opt/module/hadoop-3.2.0为我的hadoop安装路径,必须要写绝对路径~
3. namenode进入安全模式
2019-02-03 17:26:09,459 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable rm: Cannot delete /user/hehuan/mapreduce/wordcount/output. Name node is in safe mode.
解决办法:
hadoop dfsadmin –safemode leave