Directory Permission Change Not Working

Solution 1:

I know it's not quite answering the question as asked, but from the looks of things, adding any users which need that access to group "vboxsf" might actually be the better way to go. The command:

usermod -aG vboxsf user

should do the trick, assuming the user you want to give access to is named "user". After that, try writing to the directory as the user. I think it should work.

Solution 2:

As the directory is shared by the host, the permission change should be applied on the host system (Mac) not the guest (Ubuntu) where the folder is mounted. The method of adding the user to the group vboxsf won't work in this special case I think because the Mac won't know about the Ubuntu user so the chmod 777 (rwxrwxrwx) is the way to go.