Two accounts, one box --
I have administrator and personal accounts on my laptop. I installed ubuntu18.04 on the administrator account. There does not seem to be any way for the personal account to access the administrators ubuntu. (1) is it possible; (2) if not, can it be made so; (3) if it cannot, this would probably be a good idea (multiple account access to a single installation). If you think about it, this is the way "real" linux installations are.