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:
id -u nginx
The error output from the command was:
id: nginx: no such user
Vagrant版本：1.9.1
Virtualbox版本：5.1.14
已经尝试了这个并且它没有奏效：
sudo ln -s /opt/VBoxGuestAdditions-4.3.10/lib/VBoxGuestAdditions /usr/lib/VBoxGuestAdditions
ln: /usr/lib/VBoxGuestAdditions: File exists