hadoop学习笔记以及遇到的坑整理(长期更新)

1.要看官方文档

http://hadoop.apache.org/docs/current/

2.start-dfs.sh时提示rcmd: socket: Permission denied

解决方法：
在/etc/pdsh下面新建文件rcmd_default，写入ssh，而后回车，记得必定要输入一个回车符另起一行，否则会提示ssh exit with code 1

3.org.apache.hadoop.hdfs.server.datanode.DataNode: Problem connecting to server: server3/192.168.2.107:8020

各个节点的配置文件保存一致，这里由于fs.defaultFS设置错误致使，datanode找不到namenode

4.hadoop执行jar

idea生成可执行jar包：https://www.cnblogs.com/blog5277/p/5920560.html

hadoop执行命令：bin/hadoop jar xxx.jar arg1 arg2   (single node)

5.hadoop java api文档

http://hadoop.apache.org/docs/r3.1.0/api/index.html

6.org.apache.hadoop.hdfs.server.common.InconsistentFSStateException: Directory /tmp/hadoop-kevin/dfs/name is in an inconsistent state: storage directory does not exist or is not accessible.

很明显/tmp下是按期清理的 因此咱们要把dfs/name设置到其余位置

core-site.yml

<property> 　　<name>hadoop.tmp.dir</name> 　　<value>/data/hadoop/hadoop-${user.name}</value> 　　<description>A base for other temporary directories.</description> </property>