This article will get you started with performing Firmware Over the Air updates of modules, using just local AT Commands.

Download file(s) to FFS
Initiate FOTA firmware update process from FFS
Initiate JRC update process from FFS
Initiate Java Application OTAP update process from FFS

Module families accepting Java (or any file) Download to FFS

List contents of and free space on FFS, along with file stats
Rename an existing closed File
Remove an existing File from FFS

Linux examples; using Terminal windows to copy files and install Module firmware / Java applications.

Covers the AT^SFSA changes introduced with the recent security tightening of EHSx, ELS61 and PLS62 products.

See related articles:

https://iot-developer.thalesgroup.com/tutorial/flash-file-system-access-...
https://iot-developer.thalesgroup.com/showcase/command-mqtt-client
https://iot-developer.thalesgroup.com/tutorial/data-transfer-methods-mqt...