Question: How tp add a rule using firewall-cmd to drop/reject specific IP connecting to the server? This can be used as an added security on the server.

firewall-cmd is the most common method of managing firewalld configurations (both running as well as permanent). This tool is a part of the firewalld package.

docker 容器暴露的端口不会因 firewalld 防火墙策略阻断！

最近发现一个问题，docker run 了几个容器，暴雷了 8080， 9090 等等几个端口，一直以为 CentOS 有 firewalld 防火墙在，加了这些端口只允许内网访问，就可以高枕无忧了。
结果有次查看 netstat，居然有一些国外的 IP 连接。这才知道原来有防火墙，容器也不安全！