Base de connaissances

Grafana Loki is a lighter-weight alternative to the ELK Stack, designed to index only log metadata (not full-text content), resulting in significantly lower resource requirements — a practical choice for smaller VPS deployments.

Why Loki Uses Fewer Resources Than ELK

Unlike Elasticsearch, which fully indexes log content for powerful full-text search, Loki indexes only labels (metadata like source, level, service name), storing the actual log content more cheaply — a deliberate trade-off reducing resource requirements substantially, particularly relevant for smaller-scale VPS deployments.

Prerequisites

• Ubuntu 22.04/24.04 VPS: 2 vCPU, 2-4 GB RAM (much lighter than ELK)
• Docker installed
• Grafana already installed (see How to Set Up Prometheus and Grafana for VPS Monitoring) for visualization

Step 1 — Run Loki

docker run -d \
  --name loki \
  --restart unless-stopped \
  -p 3100:3100 \
  -v loki-data:/loki \
  grafana/loki:latest

Step 2 — Verify Loki Is Running

curl http://localhost:3100/ready

Step 3 — Install Promtail (Loki's Log Shipper)

docker run -d \
  --name promtail \
  --restart unless-stopped \
  -v /var/log:/var/log:ro \
  -v $(pwd)/promtail-config.yml:/etc/promtail/config.yml \
  grafana/promtail:latest \
  -config.file=/etc/promtail/config.yml

Step 4 — Configure Promtail

nano promtail-config.yml

server:
  http_listen_port: 9080

positions:
  filename: /tmp/positions.yaml

clients:
  - url: http://YOUR_LOKI_SERVER_IP:3100/loki/api/v1/push

scrape_configs:
  - job_name: system
    static_configs:
      - targets:
          - localhost
        labels:
          job: varlogs
          __path__: /var/log/*.log

Step 5 — Add Loki as a Data Source in Grafana

In Grafana: Connections → Data Sources → Add Data Source → Loki, enter your Loki server's URL.

Step 6 — Explore Logs in Grafana

Under Explore, select the Loki data source and use LogQL (Loki's query language, similar in spirit to Prometheus's PromQL) to search and filter logs.

Basic LogQL Query Examples

{job="varlogs"} |= "error"

{job="varlogs"} | json | level="error"

Building Log-Based Dashboards

Since Loki integrates directly with Grafana, you can combine log-derived panels alongside your existing Prometheus metrics dashboards in one unified view — a significant convenience if already using Grafana for metrics.

Setting Log Retention

limits_config:
  retention_period: 720h

Configure retention based on your storage capacity and actual need to look back at historical logs — shorter retention reduces storage costs.

When to Choose Loki Over ELK

Common Errors

Promtail runs but no logs appear in Grafana — verify the Loki URL in Promtail's config is correct and reachable, and check Promtail's own logs for connection errors.

Continue Reading

• How to Set Up Prometheus and Grafana for VPS Monitoring
• How to Set Up Centralized Logging with the ELK Stack (Elasticsearch, Logstash, Kibana)
• Structured Logging Best Practices for Easier Debugging

Browse more articles in Advanced Observability & Incident Management.