Hi @Mukhopadhyay, Sugato Greetings! Welcome to Microsoft Q&A forum. Thank you for posting the question here.
The SWU file you are referring is only mandated for Delta updates feature in Device update for IoT Hub. Delta updates allow you to generate a small update that represents only the changes between two full updates - a source image and a target image. This approach is ideal for reducing the bandwidth used to download an update to a device, particularly if there have been only a few changes between the source and target updates.
Please note that, in addition to the Delta updates feature, Device Update for Azure IoT Hub supports image-based, package-based, and script-based updates. The following articles will help you as a reference guide on how to achieve this updates.
- Device Update for Azure IoT Hub using the Raspberry Pi 3 B+ reference image
- Device Update for Azure IoT Hub using the package agent on Ubuntu Server 18.04 x64
The above two approaches use JSON file to formulate a template needed for the device updates.
Hope this helps! Please let us know if you have additional questions in the comments below and we would be glad to help you further.
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