In Hyper-V Configuration 8.3. When using the Ubuntu 18.04.1 Quick Create install, there needs to be an option to specify HDD size!
I ran out of disk space on my Ubuntu setup because Hyper-V only provided it a 11GB storage.
You can go back and expand the hard disk, but this does not translate right over into Ubuntu because it will not automatically take up the allocated space.
Now I have to track down the ISO to boot up in Hyper-V to see if I can manage the disk drive. This should all be native to Hyper-V.
In fact the ISO of Ubuntu it downloads she stored so that it can accessed later for instance such as this where a LIVE iso is needed.