📦 Safe USB Flash Backup Script

A reliable Bash script for secure and efficient synchronization of a local directory to a USB flash drive using rsync.

Unlike simple copy commands, this script acts defensively: it validates hardware states, calculates data payloads, checks boundaries, and prevents data loss before a single byte is written.

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✨ Key Features

• 🔒 Hardware Mount Validation: Ensures the specified USB flash drive is genuinely mounted at the target path before initiating execution to prevent writing to the root filesystem.
• 📊 Pre-flight Storage Calculation: Dynamically measures the source directory size using du and compares it against the exact available space on the flash drive via df. If space is insufficient, it aborts gracefully.
• 🔄 Intelligent Synchronization (rsync): Utilizes rsync mirroring (--delete) to keep your backup atomic and clean, ensuring files deleted from the source are also pruned from the destination.
• 📈 Global Progress Tracking: Employs --info=progress2 to provide a clean, modern, single-line global transfer progress bar instead of cluttering the terminal output with thousands of individual file names.
• 🛡️ Defensive Error Handling: Implements precise exit status trapping (set -e paired with selective set +e) to intercept and report rsync runtime anomalies safely.

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🛠️ System Dependencies

The script relies on standard Linux utilities. Before running, ensure you have the following installed (standard on almost all distributions):

• bash (interpreted shell, version 4.0+)
• rsync (fast, versatile, remote and local file-copying tool)
• numfmt (utility to convert numbers to/from human-readable formats, part of GNU coreutils)
• coreutils (provides native df, du, and mkdir commands)

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🚀 Getting Started & Configuration

1. Clone the Repository

git clone [https://github.com/your-username/your-repo-name.git](https://github.com/your-username/your-repo-name.git)
cd your-repo-name

2. Configure Your Paths

Open backup-flash.sh in your favorite text editor (e.g., nano or sublime) and locate the Configuration block. Modify the values to match your specific environment:

# ===== Configuration =====

SRC="$HOME/Dir/"             # The local folder you want to back up
FLASH_LABEL="BACKUP_USB"     # The volume label/name of your USB drive
BACKUP_DIR="DIR-SYNC"        # The target folder name inside the USB drive

# =========================