現象 vagrant upで仮想マシンを起動するときに以下のようなメッセージが出て、共有フォルダのマウントに失敗することがあります。 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`,dmode=777,fmode=666 v