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SD Card Image Comparison

language
eng
date
Jan 7, 2026
slug
compareSDCard
author
status
Public
tags
Hardware
SDCard
summary
Verifying whether an OS boot image is valid by comparing images stored on SD cards.
type
Post
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ChatGPT Image 2026๋…„ 1์›” 7์ผ ์˜ค์ „ 02_58_11.png
category
DevBoard
updatedAt
Jan 6, 2026 05:59 PM
Since I sell embedded products in a B2B environment, I use eMMC and SD cards as storage media for the operating system and system images. For mass production and delivery, the same image must be written to a large number of eMMC modules and SD cards.
However, when issues arise in some delivered products, it becomes necessary to check whether the images stored on the eMMC or SD cards are corrupted or inconsistent. To do this, I performed an image comparison between SD cards taken from a normal (working) product and a problematic one.
Using a third Linux PC, I mounted two SD cardsโ€”one known-good and one suspected to be faultyโ€”and compared their contents to verify whether the image itself was damaged or had any inconsistencies.

Mounting

sudo mkdir -p /mnt/sdf1   # boot1 ํŒŒํ‹ฐ์…˜์šฉ
sudo mkdir -p /mnt/sdf2   # root1 ํŒŒํ‹ฐ์…˜์šฉ
sudo mount /dev/sdf1 /mnt/sdf1    # sde1 โ†’ /mnt/sde1
sudo mount /dev/sdf2 /mnt/sdf2    # sde2 โ†’ /mnt/sde2

sudo mkdir -p /mnt/sdg1   # boot1 ํŒŒํ‹ฐ์…˜์šฉ
sudo mkdir -p /mnt/sdg2   # root1 ํŒŒํ‹ฐ์…˜์šฉ
sudo mount /dev/sdg1 /mnt/sdg1    # sde1 โ†’ /mnt/sde1
sudo mount /dev/sdg2 /mnt/sdg2    # sde2 โ†’ /mnt/sde2

Comparison

sudo sh -c '
  cd /mnt/sdg2 && \
  find . -path "./System Volume Information" -prune -o -type f -exec sha256sum {} + | sort \
  > /home/jamesyeon/hash_sdg2.txt
'
sudo sh -c '
  cd /mnt/sdf2 && \
  find . -path "./System Volume Information" -prune -o -type f -exec sha256sum {} + | sort \
  > /home/jamesyeon/hash_sdf2.txt
'
sudo diff -u ~/hash_sdg2.txt ~/hash_sdf2.txt

sudo sh -c '
  cd /mnt/sdg1 && \
  find . -path "./System Volume Information" -prune -o -type f -exec sha256sum {} + | sort \
  > /home/jamesyeon/hash_sdg1.txt
'
sudo sh -c '
  cd /mnt/sdf1 && \
  find . -path "./System Volume Information" -prune -o -type f -exec sha256sum {} + | sort \
  > /home/jamesyeon/hash_sdf1.txt
'
sudo diff -u ~/hash_sdg1.txt ~/hash_sdf1.txt



sudo rsync -avc --exclude='System Volume Information/**' \
           --exclude='var/lib/systemd/random-seed' \
           /mnt/sdg2/ /mnt/sdf2/
ย 

Unmount

sudo umount /mnt/sdd1 /mnt/sdd2
sudo umount /mnt/sdf1 /mnt/sdf2
ย 
The comparison commands themselves can be scripted and executed quickly. However, the most time-consuming part of this process is the physical action of inserting and removing the SD cards used as comparison targets. This step cannot be automated. As a result, comparing dozens of SD cards requires dozens of repetitive manual actions.
ย 
โ† Back

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