Centos7引入了新的防火墙firewalld, iptables被取代

安装Centos 7之后，使用下面的命令来管理iptables，也就是linux经典的防火墙

$ sudo service iptables status

Redirecting to /bin/systemctl status iptables.service
iptables.service
Loaded: not-found (Reason: No such file or directory)
Active: inactive (dead)

说找不到这个服务，这就奇怪了，这个向来都是系统内置，不需要另外安装的，这怎么不存在，后来上网查了查，才知道

自centos7之后引入了新的服务叫做firewalld

关于firewall的简单的介绍：

The dynamic firewall daemon firewalld provides a dynamically managed firewall with support for network “zones” to assign a level of trust to a network and its associated connections and interfaces. It has support for IPv4 and IPv6 firewall settings. It supports Ethernet bridges and has a separation of runtime and permanent configuration options. It also has an interface for services or applications to add firewall rules directly.

更多的关于firewalld的知识，强参看：

https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Security_Guide/sec-Using_Firewalls.html