错误信息：

Vagrant was unable to mount VirtualBox shared folders. This is usually
because the filesystem "vboxsf" is not available. This filesystem is
made available via the VirtualBox Guest Additions and kernel module.
Please verify that these guest additions are properly installed in the
guest. This is not a bug in Vagrant and is usually caused by a faulty
Vagrant box. For context, the command attempted was:

mount -t vboxsf -o uid=1000,gid=1000 vagrant /vagrant

The error output from the command was:

mount: unknown filesystem type 'vboxsf'

解决方法：

# 安装 vbguest 插件
vagrant plugin install vagrant-vbguest
# 重启虚拟机
vagrant box reload