Hadoop连不上节点端口？

原因：DataNode 47系统cpu过高重启后，出现下述问题。
[www.linuxidc.com@Hadoop48 ~]$ fs -rm 1.txt
rm: org.apache.hadoop.hdfs.server.namenode.SafeModeException: Cannot delete /user/zhouhh/1.txt. Name node is in safe mode.
进入了安全模式？
重启hadoop也不能解决。只好强制离开安全模式。

 [www.linuxidc.com@Hadoop48 hadoop-1.0.3]$ hadoop dfsadmin -safemode leave
 [www.linuxidc.com@Hadoop48 ~]$ fs -rm 1.txt
 Deleted hdfs://Hadoop48:54310/user/zhouhh/1.txt

删除文件成功。

 [www.linuxidc.com@Hadoop48 ~]$ hadoop fs -put 1.txt .
 12/06/18 18:14:53 INFO hdfs.DFSClient: Exception in createBlockOutputStream 192.168.10.46:50010 java.io.IOException: Bad connect ack with firstBadLink as 192.168.10.47:54313
 12/06/18 18:14:53 INFO hdfs.DFSClient: Abandoning block blk_6739152855033658770_1512
 12/06/18 18:14:53 INFO hdfs.DFSClient: Excluding datanode 192.168.10.47:54313
 到47上看，jps 进程都在。
 [www.linuxidc.com@Hadoop47 ~]$ jps
 4067 HQuorumPeer
 3913 TaskTracker
 3803 DataNode
 9951 Jps
 4216 HRegionServer
 查看端口，也都在监听：
 [www.linuxidc.com@Hadoop47 ~]$ netstat -antp |grep 543
 (Not all processes could be identified, non-owned process info
 will not be shown, you would have to be root to see it all.)
 tcp 0 0 0.0.0.0:54313 0.0.0.0:* LISTEN 3803/java
 tcp 0 0 0.0.0.0:54314 0.0.0.0:* LISTEN 3803/java
 tcp 0 0 0.0.0.0:54315 0.0.0.0:* LISTEN 3803/java
 tcp 0 0 192.168.10.47:48636 192.168.10.48:54310 TIME_WAIT -
 tcp 0 0 192.168.10.47:48639 192.168.10.48:54310 TIME_WAIT -
 tcp 0 0 192.168.10.47:59779 192.168.10.48:54311 ESTABLISHED 3913/java
 tcp 0 0 192.168.10.47:55475 192.168.10.48:54310 ESTABLISHED 3803/java

重启hadoop，没有解决问题。困惑了很久，忽然想到了防火墙。
有时系统没有配好防火墙，重启后导致防火墙屏蔽了hadoop的端口。测试时可以将防火墙全部关闭。

[root@Hadoop47 ~]# iptables -L
Chain INPUT (policy ACCEPT)
target prot opt source destination
RH-Firewall-1-INPUT all -- anywhere anywhere

Chain FORWARD (policy ACCEPT)
 target prot opt source destination
 RH-Firewall-1-INPUT all -- anywhere anywhere

Chain OUTPUT (policy ACCEPT)
 target prot opt source destination

Chain RH-Firewall-1-INPUT (2 references)
 target prot opt source destination
 ACCEPT all -- anywhere anywhere
 ACCEPT icmp -- anywhere anywhere icmp any
 ACCEPT esp -- anywhere anywhere
 ACCEPT ah -- anywhere anywhere
 ACCEPT udp -- anywhere 224.0.0.251 udp dpt:mdns
 ACCEPT udp -- anywhere anywhere udp dpt:ipp
 ACCEPT tcp -- anywhere anywhere tcp dpt:ipp
 ACCEPT all -- anywhere anywhere state RELATED,ESTABLISHED
 ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:ssh
 REJECT all -- anywhere anywhere reject-with icmp-host-prohibited

关闭防火墙：

[root@Hadoop47 ~]# service iptables stop
Flushing firewall rules: [ OK ]
Setting chains to policy ACCEPT: filter [ OK ]
Unloading iptables modules: [ OK ]
[root@Hadoop47 ~]# chkconfig iptables off

在生产系统中再配置域外的防火墙。

[www.linuxidc.com@Hadoop48 ~]$ fs -put 1.txt .
成功