1. 系统防火墙
关闭 service iptables stop
2. NamenodeID冲突
delete folder defined in core-site.xml
format again
3. socket conflict
查看全部 netstat -tln
查看特殊 netstat -anp | grep 9000
kill uid
修改socket in core-site.xml mapred-site.xml
4. 查看日志
hadoop目录下logs