Prometheus Tutorial – From Basics to Practical Setup

DevOps

Posted on January 3, 2026January 3, 2026 | by Rajesh Kumar

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1️⃣ What is Prometheus?

Prometheus is an open-source monitoring and alerting system designed primarily for cloud-native and Kubernetes environments, but it works equally well with VMs, bare-metal servers, and applications.

Key Characteristics

✅ Monitoring Tool
✅ Database
✅ Time-Series Database (TSDB)
✅ Cloud-native & Kubernetes core component
✅ Written in Go
✅ Runs on any OS
✅ Pull-based architecture
✅ Highly scalable & reliable

2️⃣ Prometheus as a Time-Series Database

Prometheus stores data as time-series, meaning every data point is associated with a timestamp.

Time-Series Format

(timestamp, metric_name, value, labels)

Example

Timestamp (epoch)	Metric	Value	Labels
1700000000	cpu_usage	32	name=”cpuserver1″

➡️ Each metric can have multiple labels, making Prometheus extremely powerful for filtering and aggregation.

3️⃣ Why Prometheus is Popular

Designed for modern microservices
Excellent label-based querying
Strong Kubernetes integration
Simple architecture (no external DB needed)
Large exporter ecosystem

4️⃣ Architecture & Core Components of Prometheus

🔹 1. Prometheus Server

This is the heart of the system.

It includes:

Time-Series Database (TSDB)
PromQL Engine – query language
Alerting Rules Engine
Web UI (Expression Browser)
Pull Mechanism (scrapes metrics)

🔹 2. Exporters

Exporters expose metrics in a Prometheus-friendly format.

Examples:

Node Exporter – Linux OS metrics
Blackbox Exporter – HTTP, ICMP, TCP checks
MySQL Exporter
Nginx Exporter

📌 Exporters run on targets, not on Prometheus itself.

📘 Official exporter list:
https://prometheus.io/docs/instrumenting/exporters/

🔹 3. Client Libraries

Used when applications expose their own metrics.

Supported languages:

Go
Java
Python
Node.js
.NET

🔹 4. Alertmanager

Handles alerts sent by Prometheus.

Functions:

Deduplication
Grouping
Routing
Notifications (Email, Slack, PagerDuty, etc.)

5️⃣ How Prometheus Works (Pull vs Push)

Pull-Based Model (Default)

Prometheus pulls metrics from targets
Targets expose /metrics
Prometheus decides:
- When to scrape
- How often
- Which targets

✅ Better control
✅ Easier debugging
✅ Secure & scalable

⚠️ Push is only used in special cases (via Pushgateway)

6️⃣ Getting Started – Hands-On Setup

✅ Step 1: Install & Start Prometheus Server (DONE)

Download:
https://prometheus.io/download/

Reference Guide:
https://www.devopsschool.com/blog/install-and-configure-prometheus-server-and-node-exporter-in-rhel/

Access Prometheus UI:

http://43.205.98.212:9090
Code language: JavaScript (javascript)

✅ Step 2: Setup Node Exporter on Linux Servers (DONE)

Node Exporter exposes system metrics like:

CPU
Memory
Disk
Network
Load

Example metrics endpoint:

http://43.205.98.212:9100/metrics
Code language: JavaScript (javascript)

✅ Step 3: Configure Scraping for Linux Servers

Targets:

http://43.205.98.212:9100
http://43.205.98.213:9100
http://43.205.98.214:9100
Code language: JavaScript (javascript)

🔧 Add Linux Job in `prometheus.yml`

scrape_configs:
  - job_name: "linux-nodes"
    static_configs:
      - targets:
          - "43.205.98.212:9100"
          - "43.205.98.213:9100"
          - "43.205.98.214:9100"
        labels:
          env: "production"
          role: "linux-server"
Code language: CSS (css)

Reload Prometheus:

kill -HUP <prometheus_pid>
Code language: HTML, XML (xml)

or restart service.

✅ Step 4: Visualize Metrics Using Expression Browser

Open:

http://43.205.98.212:9090
Code language: JavaScript (javascript)

Example PromQL Queries

CPU Usage

rate(node_cpu_seconds_total{mode!="idle"}[5m])
Code language: JavaScript (javascript)

Memory Usage

node_memory_MemAvailable_bytes

Disk Usage

node_filesystem_avail_bytes

📘 PromQL Examples:

7️⃣ Summary – Prometheus at a Glance

Feature	Description
Storage	Built-in Time-Series DB
Data Model	Metric + Labels
Collection	Pull-based
Query Language	PromQL
Visualization	Built-in UI + Grafana
Alerts	Prometheus + Alertmanager
Cloud Native	Kubernetes native

8️⃣ What to Learn Next 🚀

PromQL (Advanced queries)
Alert Rules & Alertmanager
Grafana Dashboards
Prometheus in Kubernetes
Federation & Remote Storage