WARN org.apache.hadoop.hdfs.server.datanode.DataNode: Problem connecting to server:

关防火墙之类的并不能解决问题，仔细思考了下，我决定先用telnet远程访问端口，成功后发现还是不能把datanode连上namenode,于是我把本地的23端口（telnet需要）也开放了，确保能本地访问。

先装个telnet,生成iptables相关规则（别没事就关防火墙）

hosts文件别出现0，0，0，0的ip(slave节点上)

yum install telnet -y

yum install telnet-server -y

yum install iptables-services -y

yum -y install xinetd

在iptables文件中开放23端口，新安装的Linux系统中，防火墙默认是被禁掉的，没有配置过任何防火墙的策略，所有不存在/etc/sysconfig/iptables文件。

systemctl stop firewalld

systemctl mask firewalld  

systemctl enable iptables

systemctl stop iptables

systemctl start iptables

systemctl restart iptables

service iptables save

vim /etc/sysconfig/iptables
# Generated by iptables-save v1.4.21 on Fri Jun 22 21:17:57 2018
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [68:9482]
-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -p icmp -j ACCEPT
-A INPUT -i lo -j ACCEPT
-A INPUT -p tcp -m state --state NEW -m tcp --dport 22 -j ACCEPT
-A INPUT -p tcp -m state --state NEW -m tcp --dport 23 -j ACCEPT
-A INPUT -j REJECT --reject-with icmp-host-prohibited
-A FORWARD -j REJECT --reject-with icmp-host-prohibited
COMMIT
# Completed on Fri Jun 22 21:17:57 2018

允许root账户登录

vi /etc/securetty
#结尾加上
pts/0  
pts/1 

重启iptables服务

systemctl restart iptables
systemctl disable firewalld
systemctl stop firewalld

systemctl start telnet.socket
systemctl start xinetd
systemctl enable xinetd
systemctl enable telnet.socket

最后验证一下：

telnet localhost 23

telnet  ip port(namenode)

对了，由于需要远程访问，所以我把master的host文件改了下

127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
0.0.0.0    spark-master

这么做是为了让远程访问可行，netstat -nltp查看，你的9000端口需要是

0.0.0.0 9000

这样所有的主机都能远程连接