Failed to mount folders in Linux guest. This is usually because the "vboxsf" file system is not available. Please verify that the guest additions are properly installed in the guest and can work properly. The command attempted was: mount -t vboxsf -o uid=`id -u vagrant`,gid=`getent group vagrant | cut -d: -f3` vagrant_data /vagrant_data mount -t vboxsf -o uid=`id -u vagrant`,gid=`id -g vagrant` vagrant_data /vagrant_data The error output from the last command was: mount: unknown filesystem type 'vboxsf'
が出た時には次のように対処します。
vagrant halt vagrant plugin install vagrant-vbguest vagrant up