[Unit]
Description=Run rtc at shutdown checking is UPS is on battery
Requires=network.target
DefaultDependencies=no
After=postfix.service
Before=shutdown.target reboot.target
[Service]
Type=oneshot
RemainAfterExit=true
ExecStart=/bin/true
ExecStop=/usr/local/bin/rtcwake

[Install]
WantedBy=multi-user.target