How to Clone a Bootable SD Card on Linux & macOS for Backup 🖥️💾

Ever needed to back up a bootable SD card for your Raspberry Pi or embedded system? Whether you're safeguarding your work or preparing for disaster recovery, cloning your SD card is a smart move. Here’s how you can do it quickly using just your terminal! 🚀

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🔹 Step 1: Identify Your SD Card

Insert the SD card and find its disk identifier:

✅ For Linux:

lsblk

✅ For macOS:

diskutil list

Look for something like /dev/sdX (Linux) or /dev/disk2 (macOS).

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🔹 Step 2: Create a Backup Image

Run this command to clone the SD card into an image file:

✅ For Linux:

sudo dd if=/dev/sdX of=~/sdcard_backup.img bs=4M status=progress

✅ For macOS (I used the full home directory path):

sudo dd if=/dev/disk2 of=/Users/[YOUR HOME DIR NAME]/sdcard_backup.img bs=4M status=progress

This creates sdcard_backup.img in your home directory.

🕒 Time Check: This took about 50 minutes on a 2018 Mac mini i7 (32GB RAM) for a 32GB SD card with Raspberry Pi OS Lite, Pi-hole, and Unbound.

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🔹 Step 3: Verify the Backup Image

Check if the backup exists and is the correct size:

ls -lh ~/sdcard_backup.img

(Optional) Mount the image to verify its contents:

hdiutil attach ~/sdcard_backup.img

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🔹 Step 4: Restore the Image to a New SD Card

1️⃣ Insert the new SD card and find its disk identifier:

✅ For Linux:

lsblk

✅ For macOS:

diskutil list

2️⃣ Unmount the SD card/s:

✅ For Linux:

sudo umount /dev/sdX*

(Use * if the disk has multiple partitions)

✅ For macOS:

diskutil unmountDisk /dev/disk2

3️⃣ Write the backup image to the new SD card:

✅ For Linux:

sudo dd if=~/sdcard_backup.img of=/dev/sdY bs=4M status=progress

(Replace /dev/sdY with the correct device name of the new SD card.)

✅ For macOS:

sudo dd if=/Users/[YOUR HOME DIR NAME]/sdcard_backup.img of=/dev/disk2 bs=4M status=progress

(In my case, /dev/disk2 was the name of my new SD card.)

🕒 Another 50 minutes later... and now I have two identical bootable SD cards! ✅

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Why Should You Backup Your SD Card?

✔️ Prevent data loss 💾 ✔️ Easily restore your system ⚡ ✔️ Save time in case of failure 🔄

Having a backup SD card ensures peace of mind when working with Raspberry Pi, embedded systems, or custom Linux builds. 🔥