Prometheus + Grafana + node_exporter

This open source stack collects metrics (Prometheus), exposes them via node_exporter, and visualizes them in Grafana. Ideal on a HolyCloud Performance VPS dedicated to monitoring, or on the monitored VPS itself for small fleets.

Prerequisites

• Linux VPS 2 GB+ RAM (4 GB if Grafana + Prometheus + multiple targets)
• Ports: 9090 (Prometheus), 3000 (Grafana), 9100 (node_exporter) — restrict with firewall
• Domain name or VPN access recommended for Grafana UI
• Backup Docker volumes or data directories

Architecture

[VPS target] node_exporter:9100
        ↓ scrape
[Prometheus] :9090  →  [Grafana] :3000 (datasource Prometheus)

Install node_exporter (on each VPS)

NODE_EXPORTER_VERSION=1.8.2
cd /tmp
curl -LO https://github.com/prometheus/node_exporter/releases/download/v${NODE_EXPORTER_VERSION}/node_exporter-${NODE_EXPORTER_VERSION}.linux-amd64.tar.gz
tar xzf node_exporter-${NODE_EXPORTER_VERSION}.linux-amd64.tar.gz
sudo cp node_exporter-${NODE_EXPORTER_VERSION}.linux-amd64/node_exporter /usr/local/bin/

systemd service:

sudo tee /etc/systemd/system/node_exporter.service << 'EOF'
[Unit]
Description=Prometheus Node Exporter
After=network.target

[Service]
User=nobody
ExecStart=/usr/local/bin/node_exporter --web.listen-address=127.0.0.1:9100
Restart=on-failure

[Install]
WantedBy=multi-user.target
EOF

sudo systemctl daemon-reload
sudo systemctl enable --now node_exporter
curl -s http://127.0.0.1:9100/metrics | head

Listen on 127.0.0.1; expose via SSH tunnel or authenticated reverse proxy.

Prometheus (Docker recommended)

sudo mkdir -p /opt/prometheus/{data,config}
sudo tee /opt/prometheus/config/prometheus.yml << 'EOF'
global:
  scrape_interval: 15s

scrape_configs:
  - job_name: node
    static_configs:
      - targets:
          - 127.0.0.1:9100
        labels:
          instance: vps-performance-01
EOF

docker run -d --name prometheus --restart unless-stopped \
  -p 127.0.0.1:9090:9090 \
  -v /opt/prometheus/config/prometheus.yml:/etc/prometheus/prometheus.yml:ro \
  -v /opt/prometheus/data:/prometheus \
  prom/prometheus:latest \
  --config.file=/etc/prometheus/prometheus.yml \
  --storage.tsdb.retention.time=15d

Add other VPS instances:

      - targets: ['10.0.0.5:9100', '10.0.0.6:9100']

Grafana

docker run -d --name grafana --restart unless-stopped \
  -p 127.0.0.1:3000:3000 \
  -v /opt/grafana:/var/lib/grafana \
  grafana/grafana:latest

First login: http://127.0.0.1:3000 → admin / admin (change the password).

1. Connections → Data sources → Prometheus
2. URL: http://prometheus:9090 if shared Docker network, otherwise http://host.docker.internal:9090 or host IP
3. Dashboards → Import → ID 1860 (Node Exporter Full)

Connect containers:

docker network create monitoring
docker network connect monitoring prometheus
docker network connect monitoring grafana

Internal datasource URL: http://prometheus:9090.

Nginx reverse proxy (HTTPS)

server {
    listen 443 ssl;
    server_name grafana.votredomaine.tld;

    location / {
        proxy_pass http://127.0.0.1:3000;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
    }
}

Enable Grafana authentication (OAuth, LDAP) in production.

Alerts (introduction)

rules.yml file:

groups:
  - name: host
    rules:
      - alert: HostHighCpu
        expr: 100 - (avg by(instance)(rate(node_cpu_seconds_total{mode="idle"}[5m])) * 100) > 90
        for: 10m
        labels:
          severity: warning

Mount the file in Prometheus and reference rule_files in prometheus.yml. Connect Alertmanager for email/Slack (beyond minimal scope).

Security

• Do not expose 9100 and 9090 on the Internet without TLS + auth
• Prefer a separate monitoring VPS that scrapes over WireGuard VPN
• Limit disk retention (retention.time, retention.size)

Verification

docker ps
curl -s http://127.0.0.1:9090/api/v1/targets | jq '.data.activeTargets[].health'

In Grafana: CPU graphs, node_memory_MemAvailable_bytes, node_filesystem_avail_bytes.

Troubleshooting

| Problem | Approach |

|----------|-------|

| Target DOWN | Firewall, wrong IP, node_exporter stopped |

| Grafana no data | Datasource URL, Docker network |

| Disk full | Reduce Prometheus retention |

Need help?

HolyCloud can confirm bandwidth quotas if you centralize scraping from many VPS instances to a single Prometheus node.