OK, that part is a little confusing to me... "any dataset under /usr without it's own dataset is part of the root dataset"... You mean, subdirectory like /usr/local ? So (referencing vermaden 's post), /usr/ports, being a dataset under /usr, does actually have its own dataset with "canmount" being on."canmount" is off. By having that off, "any dataset under /usr without it's own dataset is part of the root dataset".
If "canmount" were off there, then the evertyhing under /usr/ports/ would be part of the root dataset, is that correct? Or would it be part of the /usr dataset?zroot/usr/ports canmount on default