Vagrant error : Failed to mount folders in Linux guest

Question

I have some issues with Vagrant shared folders, my base system is Ubuntu 13.10 desktop.

I do not understand why I have this error is something that is not right conf

Answer 1

by now the mounting works on some machines (ubuntu) and some doesn't (centos 7) but installing the plugin solves it

vagrant plugin install vagrant-vbguest

without having to do anything else on top of that, just

vagrant reload