https://play.google.com/store/apps/details?id=com.softwarebakery.drivedroid https://play.google.com/store/apps/details?id=com.softwareba... I've used it succes

https://play.google.com/store/apps/details?id=com.softwarebakery.drivedroid https://play.google.com/store/apps/details?id=com.softwareba... I've used it successfully in the past to serve different Linux ISOs on the fly. It relied on certain kernel features / permissions to act as a USB mass storage device.