UbiLinux was made by others so they probably won't be able to help you here.
I don't think the Edison can boot like a PC where ISOimage can be read and booted.
There is no PC BIOS so we are in a U-boot environment ... or is it DFU?
Yocto is a great looking way to make a custom Linux bootable image for the Edison.
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Thanks for reaching out!
Ubilinux is not supported on this community as it was developed by a third party company called Emutex. They own the support of Ubilinux, so, you might be able to get more information about how to modify that OS if you contact them directly. You can contact them in https://emutex.com/about-us/contact-us.
If you'd like to use our official OS, Yocto, we would be more than glad to help you in any way we can. Image modifications are not supported by us, nevertheless, we do our best effort to answer your questions. Besides, there is a lot of official documentation provided by Yocto project. In case you are interested in this OS and learning how to modify it, I'd suggest you to start by reading Yocto's Mega Manual: http://www.yoctoproject.org/docs/1.7.3/mega-manual/mega-manual.html.
I hope this information helps you,