Re: File permissions on directories on NAS
I assume your NAS exports NFS shares. NFS, like all UNIX filesystems, stores ownerships as numeric IDs, irrespective of username. The primary UID in Ubuntu is 1000 (you can verify your UID with the command 'id'). In Macs, it's 500.
So the Mac box creates directories owned by 500 and the Ubuntu machine creates directories owned by 1000. Each are read-only for the other. There are many ways you could reconcile that: changing UIDs to match, adding both users to a group with rw access, or playing with Access Control Lists. It all depends on the degree of control you have over your NAS. So the question is: what are you running exactly?
husband@wife$ make sandwich
husband@wife$ sudo make sandwich