Vagrant 启动报错：the "vboxsf" file system is not available

有时候启动vagrant的时候会出现以下错误：

default: Checking for guest additions in VM...
default: No guest additions were detected on the base box for this VM! Guest
default: additions are required for forwarded ports, shared folders, host only
default: networking, and more. If SSH fails on this machine, please install
default: the guest additions and repackage the box to continue.
default: This is not an error message; everything may continue to work properly,
default: in which case you may ignore this message.
default: Setting hostname...
default: Configuring and enabling network interfaces...
default: Mounting shared folders...
default: /vagrant => D:/opt/Vagrant/VWOS
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 /vagrant
mount -t vboxsf -o uid=`id -u vagrant`,gid=`id -g vagrant` vagrant /vagrant

vagrant ssh登陆后发现共享文件夹没了，需要在vagrant里执行以下命令。

sudo /etc/init.d/vboxadd setup