设置CentOS防火墙开放端口
在我们使用CentOS系统的时候，CentOS防火墙有时是需要改变设置的。CentOS防火墙默认是打开的，设置CentOS防火墙开放端口方法如下：
打开iptables的配置文件：
vi /etc/sysconfig/iptables
修改CentOS防火墙时注意：一定要给自己留好后路,留VNC一个管理端口和SSh的管理端口
下面是一个iptables的示例：
# Firewall configuration written by system-config-securitylevel
# Manual customization of this file is not recommended.
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
:RH-Firewall-1-INPUT - [0:0]
-A INPUT -j RH-Firewall-1-INPUT
-A FORWARD -j RH-Firewall-1-INPUT
-A RH-Firewall-1-INPUT -i lo -j ACCEPT
-A RH-Firewall-1-INPUT -p icmp Cicmp-type any -j ACCEPT
-A RH-Firewall-1-INPUT -p 50 -j ACCEPT
-A RH-Firewall-1-INPUT -p 51 -j ACCEPT
-A RH-Firewall-1-INPUT -m state Cstate ESTABLISHED,RELATED -j ACCEPT
-A RH-Firewall-1-INPUT -m state Cstate NEW -m tcp -p tcp Cdport 53 -j ACCEPT
-A RH-Firewall-1-INPUT -m state Cstate NEW -m udp -p udp Cdport 53 -j ACCEPT
-A RH-Firewall-1-INPUT -m state Cstate NEW -m tcp -p tcp Cdport 22 -j ACCEPT
-A RH-Firewall-1-INPUT -m state Cstate NEW -m tcp -p tcp Cdport 25 -j ACCEPT
-A RH-Firewall-1-INPUT -m state Cstate NEW -m tcp -p tcp Cdport 80 -j ACCEPT
-A RH-Firewall-1-INPUT -m state Cstate NEW -m tcp -p tcp Cdport 443 -j ACCEPT
-A RH-Firewall-1-INPUT -j REJECT Creject-with icmp-host-prohibited
COMMIT
修改CentOS防火墙需要注意的是，你必须根据自己服务器的情况来修改这个文件。
举例来说，如果你不希望开放80端口提供web服务，那么应该相应的删除这一行：
-A RH-Firewall-1-INPUT -m state Cstate NEW -m tcp -p tcp Cdport 80 -j ACCEPT
全部修改完之后重启iptables:
service iptables restart