Update README.md to include project overview, features, quick start guide, and development instructions

README.md

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 # backup-client
 
+A containerized SSH backup server built on Alpine Linux, designed to provide secure remote backup access using SSH/SFTP protocols.
+
+## Features
+
+- 🔐 **Secure SSH Access**: Automated SSH server setup with configurable authentication
+- 🐳 **Docker Ready**: Multi-architecture support (linux/amd64, linux/arm64)
+- 📦 **BorgBackup Integration**: Built-in backup solution support
+- ⚙️ **Dynamic Configuration**: Real-time SSH config monitoring and reloading
+- 🔄 **CI/CD Pipeline**: Automated builds via Drone CI
+
+## Quick Start
+
+```bash
+docker run -p 20022:20022 -v /backup/data:/home/backup safebox/backup-client
+
+Configuration
+Environment Variables
+Variable	Default	Description
+SSH_PORT	20022	SSH server listening port
+SSH_USER	backup	Backup user name
+SSH_PASSWORD	backup	User password for authentication
+
+How it Works
+The container automatically:
+
+User Setup: Creates the backup user with configured credentials
+SSH Configuration: Generates host keys (RSA and Ed25519) if not present
+Server Start: Launches SSH daemon with SFTP support
+Monitoring: Watches for configuration changes and reloads SSH server as needed
+Key Components
+Dockerfile: Alpine-based image with OpenSSH, su-exec, and BorgBackup
+start_backup.sh: Main entrypoint script handling SSH setup and monitoring
+.drone.yml: CI/CD pipeline for multi-architecture builds
+Architecture
+┌─────────────────┐    ┌──────────────────┐    ┌─────────────────┐
+│   SSH Client    │───▶│  Docker Container │───▶│  Backup Storage │
+│  (Your backup   │    │   (Alpine Linux)  │    │   (/home/backup)│
+│   application)  │    │                   │    │                 │
+└─────────────────┘    └──────────────────┘    └─────────────────┘
+                              │
+
+│  (Your backup   │    │   (Alpine Linux)  │    │   (/home/backup)│
+Security Features
+Host Key Persistence: SSH host keys are generated once and persisted
+Configurable Authentication: Supports both password and public key authentication
+User Isolation: Runs SSH daemon as non-root user
+SFTP Subsystem: Secure file transfer protocol support
+Development
+Building Locally
+Testing
+CI/CD
+The project uses Drone CI for automated builds:
+
+Development builds: Push to registry.dev.format.hu/backup-client
+Release builds: Tag events push to safebox/backup-client on DockerHub
+Multi-architecture: Supports both AMD64 and ARM64 platforms
+Contributing
+Fork the repository
+Create a feature branch
+Make your changes
+Test the Docker build
+Submit a pull request
+License
+This project is open source. Please check the license file for details.
+