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linux中mysql数据库外部无法访问解决
今天在虚拟机CentOS系统中安装了mysql数据库，可是安装成功后外部却无法访问。找了好长时间才找到是由于防火墙设置造成的，现将解决过程写出来分享一下。首先，检查了mysql的权限，已经设置过了。且服务也已经启动，在localhost能够成功登陆。iptables防火墙也开启了5506端口（我安装mysql的端口喜欢采用5506，而非默认的3306）。
然后，我在本地环境链接我虚拟机里面的数据库时怎么也链接不上，提示2003的错误码信息。这个是由于网络连接不上造成的。使用SQLyog采用ssh的方式能够连接上数据库，这又说明网络是通的。然后检查用户的权限已经设置过“%”的登陆权限了。最后，我到虚拟机里面查看防火墙的状态，如下：
Chain RH-Firewall-1-INPUT (2 references) num target prot opt source destination
1 ACCEPT all -- 0.0.0.0/0 0.0.0.0/0
2 ACCEPT icmp -- 0.0.0.0/0 0.0.0.0/0 icmp type 255 3 ACCEPT esp -- 0.0.0.0/0 0.0.0.0/0
4 ACCEPT ah -- 0.0.0.0/0 0.0.0.0/0
5 ACCEPT udp -- 0.0.0.0/0 224.0.0.251 udp dpt:5353 6 ACCEPT udp -- 0.0.0.0/0 0.0.0.0/0 udp dpt:631 7 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:631 8 ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED 9 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:22 10 REJECT all -- 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibited 11 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:80 12 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:5506
我就纳闷了，怎么防火墙是接受5506端口的，可就是连接不上数据库呢。。。就在这时想到了ssh是可以连接上的。所以防火墙22的端口肯定是通的。那为什么5506的端口就不行了。 突然发现了我设置的防火墙在
10 REJECT all -- 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibited
后面，我猜想估计就是这个原因，马上把开启的端口设置放到了reject的上面，重启防火墙。搞定了！
总结：设置防火墙的时候千万要注意，不要将accept的设置放到了reject的后面，这样就可以避免防火墙设置无效的情况发生。
友情提示：不要忘记重启防火墙，呵呵！
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