systemctl可以管理远端服务器上的服务
# systemctl --help
-H --host=[USER@]HOST
Show information for remote host
示例：
# systemctl -H node-4 status ntpd
Warning: Permanently added 'node-4' (ECDSA) to the list of known hosts.
ntpd.service - Network Time Service
Loaded: loaded (/usr/lib/systemd/system/ntpd.service; enabled)
Active: active (running) since 五 2015-06-05 20:07:16 CST; 2 days ago
Main PID: 13192
CGroup: /system.slice/ntpd.servicee