Huawei S7721u Recovery Image Verify Failed Repack ((top)) -

Feature brief — "Huawei S7721U: Recovery Image Verify Failed — Repack"

4.1 Via TFTP from U-Boot

Interrupt the boot process (press Ctrl+C or f during countdown). At the HI_SILICON_V000# prompt:

# Set network parameters
setenv ipaddr 192.168.1.10
setenv serverip 192.168.1.100
setenv netmask 255.255.255.0
2. Background
1. Executive Summary
The Huawei S7721U (often a distribution switch or ONT/CPE device) may encounter a “Recovery Image Verify Failed” error during firmware updates or recovery mode operations. This report explains the root cause, the security mechanism behind the failure, and the repack procedure required to bypass or correct the verification error.
3.2 Extracting the Original Recovery Image
First, unpack the main bin file:
binwalk -e S7721UV100R001C02SPC123.bin

Navigate to the extracted folder. Look for a file named recovery.img or a SquashFS filesystem with offset 0x200000.
Alternatively, from a working S7721U:
dd if=/dev/mtd2 of=/tmp/original_recovery.img bs=64k

Step 4: Transfer the Repacked Recovery Image to the Device
Set up a TFTP server and transfer the repacked recovery image to the Huawei S7721U device. You can use tools like tftp or SolarWinds TFTP Server to facilitate the transfer.
Step 3: Padding to original size (e.g., 8MB)
truncate -s 8M repacked_recovery.img

Method B: Using HuaweiImageTool (Python) huawei s7721u recovery image verify failed repack

# Clone the tool (example repo)
git clone https://github.com/Someone42/huawei-image-tool