hadoop使用bin/start_all.sh命令之后，使用jps发现datanode无法启动
This problem comes when Datanode daemon on the system does not start.check the started daemons using "jps" command.
If it in not started,start Datanode daemon manually by using the command:
bin/hadoop-daemon.sh start datanode.
但是启动datanode之后，使用 hadoop dfsadmin -report 命令验证hadoop是否启动成功的时候，仍然显示如下错误信息：
INFO ipc.Client: Retrying connect to server: hadoop_master/192.168.3.34:9000. Already tried 0 time(s).
INFO ipc.Client: Retrying connect to server: hadoop_master/192.168.3.34:9000. Already tried 1 time(s).
。。。。。。。。
INFO ipc.Client: Retrying connect to server: hadoop_master/192.168.3.34:9000. Already tried 8 time(s).
Delete your log file and the file which your entered in "dfs.data.dir" property file in hdfs.site.xml .Format the system and start all your daemons again.This might solve your problem.
此问题属于 dataNode连不上nameNode