Linux Monitor

A full-stack, real-time Linux system monitoring platform built with Java Spring Boot, PostgreSQL, Python, React, and Docker. Inspired by professional tools like Grafana and Zabbix.

Screenshots

Login screen — supports username/password and Google OAuth2

Dashboard Client — real-time metrics, graphs, and process table

Dashboard Admin — real-time metrics, graphs, and process table

Dashboard Guest — real-time metrics, graphs, and process table

Admin panel — user management, role control, audit log

Features

Real-time monitoring — CPU, RAM, Network RX/TX refreshed every 3 seconds
Time-series persistence — all metrics saved to PostgreSQL every 5 seconds
Live graphs — CPU history chart + mini charts for RAM, Network RX/TX
Top processes — live process table sorted by CPU usage (reads from Linux /proc)
JWT authentication — stateless token-based auth with BCrypt password hashing
Google OAuth2 — login with Google account, auto-creates local user on first login
Role-based access — Admin, Moderator, Client, and Guest with different permissions
Guest preview — unregistered users see live CPU/RAM with locked overlays on restricted data
User registration — create account directly from the login screen
Admin panel — manage users, change roles, ban/unban, system summary stats
Audit log — every admin action logged with timestamp, actor, and target
Dockerized — single docker compose up --build starts the entire stack

Architecture

React Frontend (port 3000)
        │
        │  HTTP + JWT in Authorization header
        ▼
Spring Boot API (port 8080)
        │                    │                    │
        │ @Scheduled/5s      │ REST responses      │ OAuth2 redirect
        ▼                    ▼                    ▼
   Python stats.py      PostgreSQL 16        Google servers
   reads /proc/*        metrics + users      verify identity

The Python collector runs on a Spring @Scheduled timer — not per request. This means zero Python overhead on API calls. The API reads the latest saved value from the database — instantaneous response regardless of collection frequency.

Tech Stack

Layer	Technology
Backend	Java 21, Spring Boot 4.0.3
Security	Spring Security, JWT (jjwt 0.12.6), BCrypt, Google OAuth2
Database	PostgreSQL 16
ORM	Spring Data JPA, Hibernate 7
System collector	Python 3 (reads `/proc/stat`, `/proc/meminfo`, `/proc/net/dev`)
Frontend	React 18, Recharts, Axios
Containerization	Docker, Docker Compose
Build tool	Maven (with Maven Wrapper)

Project Structure

linux-monitor/
├── src/main/java/com/andrej/linux_monitor/
│   ├── config/
│   │   └── SecurityConfig.java          # Spring Security + CORS + OAuth2
│   ├── controller/
│   │   ├── StatsController.java         # GET /api/stats, GET /api/stats/history
│   │   ├── AuthController.java          # POST /api/auth/register, /login
│   │   └── AdminController.java         # /api/admin/* — ADMIN role only
│   ├── dto/
│   │   ├── StatsDto.java                # CPU, RAM, network, processes shape
│   │   ├── AuthResponse.java            # token, username, role
│   │   ├── LoginRequest.java
│   │   ├── RegisterRequest.java
│   │   ├── UserSummaryDto.java          # safe user data (no password)
│   │   ├── AdminStatsDto.java           # system summary for admin panel
│   │   └── RoleUpdateRequest.java
│   ├── model/
│   │   ├── MetricSnapshot.java          # metrics table entity
│   │   ├── User.java                    # users table entity
│   │   ├── Role.java                    # ADMIN | MODERATOR | CLIENT enum
│   │   └── AuditLog.java               # audit_log table entity
│   ├── repository/
│   │   ├── MetricRepository.java
│   │   ├── UserRepository.java
│   │   └── AuditRepository.java
│   ├── security/
│   │   ├── JwtUtil.java                 # generate + validate JWT tokens
│   │   ├── JwtFilter.java               # OncePerRequestFilter
│   │   └── OAuth2SuccessHandler.java    # find/create user after Google login
│   └── service/
│       ├── StatsService.java            # calls stats.py via ProcessBuilder
│       ├── MetricCollector.java         # @Scheduled — saves metrics every 5s
│       ├── AuthService.java             # register + login logic
│       ├── AdminService.java            # user management + audit log
│       ├── OAuth2UserService.java       # loads Google user info
│       └── UserDetailsServiceImpl.java  # Spring Security user loader
├── frontend/src/
│   ├── App.js                           # routing only
│   ├── constants.js                     # COLORS + API URL
│   └── components/
│       ├── Login.jsx
│       ├── Register.jsx
│       ├── Dashboard.jsx
│       ├── AdminPanel.jsx
│       ├── StatCard.jsx
│       ├── MiniChart.jsx
│       └── OAuth2Callback.jsx
├── stats.py                             # Python system metrics collector
├── Dockerfile                           # multi-stage build
├── docker-compose.yml                   # app + PostgreSQL services
└── pom.xml

Getting Started

Prerequisites

Docker and Docker Compose
Git

Run with Docker (recommended)

git clone https://github.com/AT95BL/linux-monitor.git
cd linux-monitor
docker compose up --build

API available at: http://localhost:8080
Start the frontend separately (see below)

Register your first admin user

# Register
curl -X POST http://localhost:8080/api/auth/register \
  -H "Content-Type: application/json" \
  -d '{"username":"andrej","email":"andrej@example.com","password":"YourPassword123!"}'

# Promote to admin
docker exec -it linux-monitor-db-1 psql -U andrej -d linux_monitor \
  -c "UPDATE users SET role='ADMIN' WHERE username='andrej';"

Run the frontend

cd frontend
npm install
npm start

Open http://localhost:3000

Run locally without Docker

Install Java 21, PostgreSQL 16, Python 3
Create the database:

CREATE DATABASE linux_monitor;
CREATE USER andrej WITH PASSWORD 'yourpassword';
GRANT ALL PRIVILEGES ON DATABASE linux_monitor TO andrej;
GRANT ALL ON SCHEMA public TO andrej;

Update src/main/resources/application.properties with your credentials
Run:

./mvnw spring-boot:run

API Reference

Public

Method	Endpoint	Description
`GET`	`/api/stats`	Current system metrics — CPU, RAM, network, processes
`POST`	`/api/auth/register`	Register a new user
`POST`	`/api/auth/login`	Login — returns JWT token
`GET`	`/oauth2/authorization/google`	Start Google OAuth2 login

Authenticated

Method	Endpoint	Description
`GET`	`/api/stats/history?minutes=30`	Historical metrics from database

Admin only

Method	Endpoint	Description
`GET`	`/api/admin/users`	List all users
`PUT`	`/api/admin/users/{id}/role`	Change a user's role
`PUT`	`/api/admin/users/{id}/status`	Ban or unban a user
`GET`	`/api/admin/audit`	View audit log
`GET`	`/api/admin/stats`	System summary stats

Using the token

Authorization: Bearer <your-jwt-token>

Role Permissions

Feature	Guest	Client	Moderator	Admin
Live CPU & RAM	✅	✅	✅	✅
Network stats	❌	✅	✅	✅
Process table	❌	✅	✅	✅
Metric history	❌	✅	✅	✅
View user list	❌	❌	✅	✅
Manage users	❌	❌	❌	✅
Change roles	❌	❌	❌	✅
Ban/unban users	❌	❌	❌	✅
Audit log	❌	❌	❌	✅

Database Schema

CREATE TABLE metrics (
    id           BIGSERIAL PRIMARY KEY,
    recorded_at  TIMESTAMP,
    cpu_percent  FLOAT,
    ram_used_mb  BIGINT,
    ram_total_mb BIGINT,
    ram_percent  FLOAT,
    rx_mb        FLOAT,
    tx_mb        FLOAT
);

CREATE TABLE users (
    id          BIGSERIAL PRIMARY KEY,
    username    VARCHAR UNIQUE NOT NULL,
    email       VARCHAR UNIQUE NOT NULL,
    password    VARCHAR NOT NULL,  -- BCrypt hash or 'OAUTH2_USER'
    role        VARCHAR,           -- ADMIN | MODERATOR | CLIENT
    created_at  TIMESTAMP,
    last_login  TIMESTAMP,
    active      BOOLEAN DEFAULT true
);

CREATE TABLE audit_log (
    id            BIGSERIAL PRIMARY KEY,
    performed_by  VARCHAR,
    action        VARCHAR,  -- ROLE_CHANGE | USER_BANNED | USER_UNBANNED
    target_user   VARCHAR,
    performed_at  TIMESTAMP
);

Google OAuth2 Setup

Go to console.cloud.google.com and create a project
APIs & Services → OAuth consent screen — configure app name and email
APIs & Services → Credentials → Create OAuth Client ID
- Type: Web application
- Authorized redirect URI: http://localhost:8080/login/oauth2/code/google
Add to application.properties:

spring.security.oauth2.client.registration.google.client-id=YOUR_CLIENT_ID
spring.security.oauth2.client.registration.google.client-secret=YOUR_CLIENT_SECRET
spring.security.oauth2.client.registration.google.scope=email,profile

Never commit your Client Secret to a public repository.

What I Learned

Designing a multi-layer Java backend with Spring Boot, JPA, and Spring Security
Implementing stateless JWT authentication with role-based access control
Integrating Google OAuth2 — consent screen, authorization code flow, token exchange
Using @Scheduled for background metric collection instead of per-request processing
Reading Linux kernel data directly from /proc filesystem using Python
Multi-stage Docker builds to minimize final image size
Connecting containerized services via Docker Compose internal networking (db:5432 not localhost)
Debugging CORS issues caused by Spring Security intercepting OPTIONS preflight requests
Building a Grafana-style React dashboard with component-based architecture

Author

Andrej Trožić

GitHub: @AT95BL
LinkedIn: Andrej Trožić
Portfolio: at95-portfolio.com

License

MIT License — feel free to use this project as a reference or starting point.

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Linux Monitor

Screenshots

Features

Architecture

Tech Stack

Project Structure

Getting Started

Prerequisites

Run with Docker (recommended)

Register your first admin user

Run the frontend

Run locally without Docker

API Reference

Public

Authenticated

Admin only

Using the token

Role Permissions

Database Schema

Google OAuth2 Setup

What I Learned

Author

License

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README.md

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README.md

File metadata and controls

Linux Monitor

Screenshots

Features

Architecture

Tech Stack

Project Structure

Getting Started

Prerequisites

Run with Docker (recommended)

Register your first admin user

Run the frontend

Run locally without Docker

API Reference

Public

Authenticated

Admin only

Using the token

Role Permissions

Database Schema

Google OAuth2 Setup

What I Learned

Author

License