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。
[@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。

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

删除文件成功。

[@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。 [@Hadoop47 ~]$ jps 4067 HQuorumPeer 3913 TaskTracker 3803 DataNode 9951 Jps 4216 HRegionServer 查看端口，也都在监听： [@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 anywhereChain OUTPUT (policy ACCEPT) target prot opt source destinationChain 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。

[@Hadoop48 ~]$ fs -put 1.txt .
成功