CentOS 7.x开始，CentOS开始使用systemd服务来代替daemon，原来管理系统启动和管理系统服务的相关命令全部由systemctl命令来代替。service命令只保留下了极少部分使用，大部分命令都要改用systemctl使用。
[root@localhost ~]# service iptables save
The service command supports only basic LSB actions (start, stop, restart, try-restart, reload, force-reload, status). For other actions, please try to use systemctl.
关闭防火墙
[root@localhost ~]# systemctl stop firewalld [root@localhost ~]# systemctl mask firewalld ----注销服务 Created symlink from /etc/systemd/system/firewalld.service to /dev/null.
安装iptables
[root@localhost ~]# yum install iptables Loaded plugins: fastestmirror, langpacks Loading mirror speeds from cached hostfile * base: mirrors.huaweicloud.com * extras: mirror.bit.edu.cn * updates: mirrors.huaweicloud.com Running transaction Updating : iptables-1.4.21-34.el7.x86_64 1/2 Cleanup : iptables-1.4.21-18.0.1.el7.centos.x86_64 2/2 Verifying : iptables-1.4.21-34.el7.x86_64 1/2 Verifying : iptables-1.4.21-18.0.1.el7.centos.x86_64 2/2 Updated: iptables.x86_64 0:1.4.21-34.el7 Complete!
设置iptables开机启动
[root@localhost ~]# systemctl enable iptables
重启iptables服务
systemctl restart iptables.service
再次执行保存命令，成功
[root@localhost ~]# service iptables save
iptables: Saving firewall rules to /etc/sysconfig/iptables:[ OK ]