well for some reason I can't account for root partition had not even a partition table!
some "customer partition" it was the system partition!!!
copying an image to /mnt/us I was able to dd it and surprise - what a shock - it worked! - bit misleading that message!
I frequently go years at a time without having to suffer windows and oh what joy! (not) was installing the fastboot usb driver.... (that little doozy wasted most of my time)
still all fixed now, just launcher an a few other bits - and oh more joy I'll probably have to recreate all my nested collections again.....