• 从节点datanode启动成功,但是后台查看发现未连接namenode,查看日志提示如下:

2019-02-26 13:53:16,307 WARN org.apache.hadoop.hdfs.server.datanode.DataNode: Problem connecting to server: server-21/192.168.0.21:9000
2019-02-26 13:53:22,310 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: server-21/192.168.0.21:9000. Already tried 0 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2019-02-26 13:53:23,312 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: server-21/192.168.0.21:9000. Already tried 1 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2019-02-26 13:53:24,315 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: server-21/192.168.0.21:9000. Already tried 2 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2019-02-26 13:53:25,318 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: server-21/192.168.0.21:9000. Already tried 3 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2019-02-26 13:53:26,321 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: server-21/192.168.0.21:9000. Already tried 4 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2019-02-26 13:53:27,323 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: server-21/192.168.0.21:9000. Already tried 5 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)

• 解决方式一
  删除hadoop目录下数据,dfs,log,tmp
  重新格式化namenode,重启start-dfs.sh 试试

删除hadoop目录下数据,dfs,log,tmp
[root@server-22 hadoop-2.7.7]# ll
total 112
drwxr-xr-x 2 root root 194 Mar 23 2019 bin
drwxr-xr-x 4 root root 30 Mar 23 2019 dfs
drwxr-xr-x 3 root root 20 Mar 23 2019 etc
drwxr-xr-x 2 root root 106 Mar 23 2019 include
drwxr-xr-x 3 root root 20 Mar 23 2019 lib
drwxr-xr-x 2 root root 239 Mar 23 2019 libexec
-rw-r–r-- 1 root root 86424 Feb 26 13:36 LICENSE.txt
drwxr-xr-x 2 root root 165 Feb 26 13:53 logs
-rw-r–r-- 1 root root 14978 Feb 26 13:36 NOTICE.txt
-rw-r–r-- 1 root root 1366 Feb 26 13:36 README.txt
drwxr-xr-x 2 root root 4096 Mar 23 2019 sbin
drwxr-xr-x 4 root root 31 Mar 23 2019 share
drwxr-xr-x 3 root root 26 Feb 26 13:26 tmp
[root@server-22 hadoop-2.7.7]#

• 解决方式二
  查看主节点master监听的端口
  如下:nameNode监听的是本机的ip,也就是说其他IP不监听

[root@server-21 ~]# netstat -an | grep 9000
tcp 0 0 127.0.0.1:9000 0.0.0.0:* LISTEN
tcp 0 0 127.0.0.1:9000 127.0.0.1:52430 ESTABLISHED
tcp 0 0 127.0.0.1:52430 127.0.0.1:9000 ESTABLISHED

修改/etc/hosts

[root@server-21 ~]# cat /etc/hosts
#127.0.0.1 localhost.localdomain localhost4 localhost4.localdomain4 server-21 qjw-01
#::1 qjw-01 localhost localhost.localdomain localhost6 localhost6.localdomain6 server-21
192.168.0.22 server-22
192.168.0.21 server-21 qjw-01

立即生效hosts

[root@server-21 ~]# su
[root@server-21 ~]# /etc/init.d/network restart

启动hadoop,start-dfs.sh
查看监听端口:如下,正常

[root@server-21 ~]# netstat -an | grep 9000
tcp 0 0 192.168.0.21:9000 0.0.0.0:* LISTEN
tcp 0 0 192.168.0.21:48224 192.168.0.21:9000 TIME_WAIT
tcp 0 0 192.168.0.21:9000 192.168.0.22:45798 ESTABLISHED
tcp 0 0 192.168.0.21:9000 192.168.0.21:48196 ESTABLISHED
tcp 0 0 192.168.0.21:48196 192.168.0.21:9000 ESTABLISHED
[root@server-21 ~]#

查看网页显示一切正常