启动、停止、重启、重载、检查服务：
6: service httpd start|stop|restart|reload|status
7: systemctl start|stop|restart|reload|status httpd.service

允许、禁止服务自启动：
6: chkconfig httpd on|off
7: system enable|disable httpd.service

列出服务：
6: chkconfig –list
7: systemctl list-unit-files –type=service 或 ls /etc/systemd/system/*.wants/

添加服务：
6: chkconfig httpd –add
7: systemctl daemon-reload