1.history -d 50 查看历史50行
systemctl start firewalld
2.端口 firewall-cmd --zone=public --add-port=80/tcp --permanent
firewall-cmd --reload
（2）查看防火墙状态
查看防火墙状态 systemctl status firewalld
开启防火墙 systemctl start firewalld
关闭防火墙 systemctl stop firewalld
开启防火墙 service firewalld start
若遇到无法开启
先用：systemctl unmask firewalld.service
然后：systemctl start firewalld.service