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DDIFF

Block Device Sync Utility for Linux

ddiff is a lightweight utility for block-level delta synchronization of files and raw devices (SD cards, SSDs, disk images). Instead of copying the whole image, it works on 1 MB chunks and transfers or applies only what changed — saving bandwidth and write cycles.

Ideal for backup and cloning on Raspberry Pi, host-to-host sync over SSH, and offline workflows with ZIP-based .diff packages.

Download

Prebuilt Linux binaries:

• ddiff for x86_64
• ddiff for aarch64 (ARM64 / Raspberry Pi)

After download: chmod +x ddiff and, if needed, copy it somewhere in your PATH (e.g. /usr/local/bin/). For SSH sync the binary must be available on both the local and the remote machine.

Features

• Block-level delta — only modified 1 MB chunks
• SSH — direct host-to-host synchronization
• Offline sync — hash on the target, .diff on the source, apply offline
• Zstd compression — lighter stream with --zstd
• ZIP format — .diff files contain only changed blocks
• Small footprint — suited to embedded devices

Quick start

Direct sync over SSH

ddiff /dev/sdb user@remote:/dev/sdb

Offline workflow (3 steps)

# 1. hash on the target
ddiff --makehash target.hash /dev/sdb

# 2. diff on the source
ddiff --makediff patch.diff --hash target.hash /dev/sdb

# 3. apply on the target
ddiff --writediff patch.diff /dev/sdb

Verify integrity of a file / block device against a stored hash

ddiff --testhash sdb.hash /dev/sdb

Full syntax: ddiff -h · Platforms: Linux x86_64 and aarch64 (Raspberry Pi OS, Ubuntu, Debian, …).

Distributed under the MIT License.

Disclaimer & Risk Notice

ddiff is a powerful command-line utility designed for low-level block device synchronization.

• Data Loss Risk: Improper use of this software (such as selecting the wrong output device or file) can lead to irreversible data overwriting and total data loss.
• No Warranty: This software is provided "as is", under the terms of the MIT License, without any express or implied warranties.
• User Responsibility: The author(s) shall not be held liable for any damage, data loss, or system failure resulting from the installation or use of ddiff.

Recommendation: Always double-check your drive labels (e.g., using lsblk or fdisk -l) and perform backups of critical data before executing synchronization commands.