add systemd service

ubuntu/system_service.md

@@ -0,0 +1,21 @@
+`//etc/systemd/system/filename.service`
+
+```
+[Unit]
+Description=forecast_api
+After=network.target
+
+[Service]
+ExecStart=/usr/bin/node //opt/forecast_api/index.js
+Restart=always
+User=fc_api
+Environemnt=NODE_ENV=production
+WorkingDirectory=//opt/forecast_api
+
+[Install]
+WantedBy=multi-user.target
+```
+
+`systemctl enable forecast.api`
+
+`systemctl start forecast_api.service`