基于Raspbian系统的SD卡自动克隆Shell脚本开发需求

Alright, let's tackle this two-part problem: creating a shell script to clone your OS from a USB drive (/dev/sda) to an SD card (/dev/sdb), and setting up automatic detection to trigger the script when the SD card is plugged in. Let's break this down step by step.

First, let's build a robust script that handles the cloning safely. Critical note: Double-check that /dev/sda is truly your source USB drive and /dev/sdb is the target SD card—mixing these up will erase data irreversibly. Use lsblk or fdisk -l to verify device paths before proceeding.

Here's the script (save it as /usr/local/bin/os-clone.sh):

#!/bin/bash

# Ensure we're running as root (required for block device operations)
if [ "$(id -u)" -ne 0 ]; then
    echo "This script needs root privileges. Run with sudo."
    exit 1
fi

# Define source and target devices
SOURCE="/dev/sda"
TARGET="/dev/sdb"

# Check if both devices exist
if [ ! -b "$SOURCE" ]; then
    echo "Error: Source device $SOURCE doesn't exist."
    exit 1
fi

if [ ! -b "$TARGET" ]; then
    echo "Error: Target device $TARGET doesn't exist."
    exit 1
fi

# Unmount any mounted partitions on the target to avoid conflicts
umount "${TARGET}?"* 2>/dev/null

# Handle user confirmation (adjust this based on your environment: GUI or CLI)
# Option 1: GUI confirmation (requires zenity)
if command -v zenity &> /dev/null; then
    if ! zenity --question --width=500 --text="⚠️ WARNING: This will OVERWRITE ALL data on $TARGET with the contents of $SOURCE.\n\nPlease confirm:\n- $SOURCE is your source USB drive\n- $TARGET is your target SD card\n\nDo you want to start cloning?"; then
        echo "Clone aborted by user."
        exit 0
    fi
# Option 2: CLI confirmation (launches a terminal since udev runs in the background)
else
    xterm -e "bash -c 'echo \"⚠️ WARNING: This will OVERWRITE ALL data on $TARGET with the contents of $SOURCE.\"; echo \"\"; echo \"Confirm $SOURCE = USB drive, $TARGET = SD card.\"; read -p \"Type YES to proceed, anything else to abort: \" CONFIRM; if [ \"\$CONFIRM\" = \"YES\" ]; then dd if=\"$SOURCE\" of=\"$TARGET\" bs=4M status=progress conv=fsync; else echo \"Aborted.\"; fi; read -p \"Press Enter to close this window.\"'"
    exit 0
fi

# Start cloning with dd (bs=4M speeds up the process; status=progress shows real-time updates)
echo "Starting clone from $SOURCE to $TARGET..."
dd if="$SOURCE" of="$TARGET" bs=4M status=progress conv=fsync

# Verify success
if [ $? -eq 0 ]; then
    echo "✅ Clone completed successfully!"
    zenity --info --text="Clone finished successfully! You can safely remove the SD card."
else
    echo "❌ Clone failed. Check device connections and try again."
    zenity --error --text="Clone failed! Please check device connections and try again."
    exit 1
fi

Make the script executable:

sudo chmod +x /usr/local/bin/os-clone.sh

Key Script Features: #

• Root privilege check to ensure we can modify block devices
• Device existence validation to avoid targeting non-existent hardware
• Automatic unmounting of target partitions to prevent write conflicts
• Dual confirmation options (GUI with zenity or CLI terminal) for different environments
• Real-time progress tracking with dd
• Clear success/failure notifications

To trigger the script when the SD card is inserted, we'll use udev—Linux's built-in system for managing device events. Here's how to set it up:

1. Identify your SD card's udev properties
   Plug in your SD card, then run this command to get its unique attributes:

   udevadm info --query=property --name=/dev/sdb
   

   Look for properties that uniquely identify SD cards, like ID_BUS=mmc (most SD cards use the MMC bus, unlike USB drives which use ID_BUS=usb).

2. Create a udev rule
   Create a new rule file at /etc/udev/rules.d/99-sd-card-clone.rules (the number ensures it runs after default system rules):

   # Trigger OS clone script when an SD card is inserted
   ACTION=="add", KERNEL=="sd[b-z]", SUBSYSTEM=="block", ENV{ID_BUS}=="mmc", RUN+="/usr/local/bin/os-clone.sh"
   

   • ACTION=="add": Triggers when the device is first plugged in
   • KERNEL=="sd[b-z]": Matches block devices sdb to sdz (avoids accidentally targeting the source USB drive /dev/sda)
   • ENV{ID_BUS}=="mmc": Ensures only SD cards (not other USB devices) trigger the script
   • RUN+="/usr/local/bin/os-clone.sh": Executes our cloning script

3. Reload udev rules
   Apply the new rule without rebooting:

   sudo udevadm control --reload-rules
   sudo udevadm trigger
   

Important Notes for udev: #

• udev runs scripts in a minimal background environment, so direct interactive commands (like read) won't work. This is why our script uses zenity or launches a terminal for user confirmation.
• The rule targets the main block device (sdb) instead of its partitions (sdb1, sdb2) to prevent multiple trigger events when the card is inserted.
• Test the setup by unplugging and reinserting your SD card—you should see the confirmation prompt pop up automatically.

内容的提问来源于stack exchange，提问作者Jan B