CentOS6關閉防火牆使用以下命令，
//臨時關閉
service iptables stop
//禁止開機啓動
chkconfig iptables off
CentOS7中若使用同樣的命令會報錯，
stop iptables.service
Failed to stop iptables.service: Unit iptables.service not loaded.
這是因爲CentOS7版本後防火牆默認使用firewalld，因此在CentOS7中關閉防火牆使用以下命令，
//臨時關閉
systemctl stop firewalld
//禁止開機啓動
systemctl disable firewalld
Removed symlink /etc/systemd/system/multi-user.target.wants/firewalld.service.
Removed symlink /etc/systemd/system/dbus-org.fedoraproject.FirewallD1.service.
當然，如果安裝了iptables-service，也可以使用下面的命令，
yum install -y iptables-services
//關閉防火牆
service iptables stop
Redirecting to /bin/systemctl stop iptables.service
//檢查防火牆狀態
service iptables status
Redirecting to /bin/systemctl status iptables.service
鈼iptables.service - IPv4 firewall with iptables
Loaded: loaded (/usr/lib/systemd/system/iptables.service; disabled; vendor preset: disabled)
Active: inactive (dead)
# https://blog.csdn.net/Post_Yuan/article/details/78603212