vagrant upしたら、「Vagrant::Errors::LinuxMountFailed」ってエラーが出たときの対処

vagrant upした時、下記のようなエラーが出てました。 Vagrant::Errors::LinuxMountFailed: 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 comm…