Operations & Maintenance

Routine Tasks

Change hosts / thresholds: edit config/settings.json
- hosts: e.g. ["8.8.8.8","1.1.1.1"]
- latencyThresholdMs: e.g. 70
The backend auto-reloads settings (within ~10s). If changes don’t appear, restart the service.

Service Management (systemd)

# status & logs
sudo systemctl status host-monitor
sudo journalctl -u host-monitor -n 200 -f

# restart & enable on boot
sudo systemctl restart host-monitor
sudo systemctl enable host-monitor

# stop / disable
sudo systemctl stop host-monitor
sudo systemctl disable host-monitor

Quick Diagnostics

# open port (Ubuntu)
sudo ufw allow 9090/tcp

# is the app listening?
ss -ltnp | grep :9090 || sudo lsof -iTCP:9090 -sTCP:LISTEN

# test locally
curl -v http://127.0.0.1:9090

Common Issues

Permission denied running script → chmod +x backend/scripts/ping-many.sh
Service points to /opt but repo elsewhere → update paths:

APP=/home/ubuntu/host-monitor
sudo sed -i "s|/opt/host-monitor|$APP|g" /etc/systemd/system/host-monitor.service
sed -i "s|^cd /opt/host-monitor/backend$|cd $APP/backend|" "$APP/backend/scripts/ping-many.sh"
sudo systemctl daemon-reload && sudo systemctl restart host-monitor

Optional: Docker

# view logs
docker logs -f host-monitor

# restart
docker restart host-monitor

# rebuild backend (Makefile)
make build