CentOS 7 firewall-cmd open a port permanently
[root@centos7 ~]# firewall-cmd --permanent --add-port=100/tcp
success
[root@centos7 ~]# firewall-cmd --reload
success
[root@centos7 ~]# firewall-cmd --permanent --add-port=100/tcp
success
[root@centos7 ~]# firewall-cmd --reload
success