This article excerpts from Baidu and CSDN blog
Firewall:
Firewall (Firewall), also known as protective wall is determined by Check Point founder Gil Shwed invented and introduced in 1993 the Internet (US5606668 (A) 1993-12-15). It is a network located between the internal network and the external network security system. An information security protection system, in accordance with certain rules that allow or limit the data transmitted through.
In the network, the so-called "firewall" refers to a method for the internal network and the public access network (eg Internet) separate, it is actually an isolation technology. A firewall is implementation of an access control in two networks communicate scale, it allows you to "agree" to enter your network and the data, while you "disagree" shut out people and data to maximize prevent network hackers to access your network.
Role of the firewall:
Firewall has a very good protection. Intruder must first pass through the security perimeter firewalls, in order to reach target computer. You can configure the firewall in many different levels of protection. High level of protection may prevent some services, such as video streaming and so on, but at least it's your own protection choices.
System security and optimization:
1, see the firewall service status: systemctl status firewalld turn off the firewall
2, stop firewall service: systemctl stop firewalld open the firewall
3, start the firewall service: systemctl start firewalld restart firewall
Restart the firewall service: systemctl restart firewalld to see whether the firewall boot from Kai
4, to see whether the firewall service startup: systemctl is-enabled firewalld boot from Kai firewall
5, start firewall service boot: systemctl enable firewalld.service boot disable the firewall
6, boot disable firewall service: systemctl disable firewalld.service