well... I'm not sure, if this solutions will get a bit out of hand (configuration-wise)... vboxfs shares are strange beasts, and setting the owner for apt-cache-ng -cache  to e.g. apt-cacher-ng user in  Vagrantfile is too much cognitive load for the enduser. (and I'm not sure, if this will work...) Keep it simple. Not everybody will need it, and those, who will, will have no problems with NFS folders, since they are actually faster and a better option. This is something, that works now, and maybe it's better to let users complain, rather than complicate the solution. less code is always better, imho. :)

How are my chances to me merged in master? :stuck_out_tongue: