gentoo-overlay/net-wireless/unifi/files/unifi.service

[Unit]
Description=UniFi Controller
After=network-online.target

[Service]
Type=simple
User=unifi
Group=unifi
WorkingDirectory=/usr/lib/unifi
ExecStart=/usr/bin/java -Djava.library.path= -Dorg.xerial.snappy.tempdir=/usr/lib/unifi/tmp -jar /usr/lib/unifi/lib/ace.jar start
ExecStop=/usr/bin/java -Djava.library.path= -Dorg.xerial.snappy.tempdir=/usr/lib/unifi/tmp -jar /usr/lib/unifi/lib/ace.jar stop

[Install]
WantedBy=network.target