title: Vagrant was unable to mount VirtualBox shared folders
body: <p>Current setup: <strong>Virtualbox 5.1.20</strong> with <strong>Vagrant 1.9.3</strong></p>
  
  <p>Previous working setup: <strong>Virtualbox 5.1.18</strong> with <strong>Vagrant 1.9.3</strong></p>
  
  <p>I installed the latest version of Virtualbox and tried to start my VM. The folder mounting has stopped working. The same folder mounting works fine in <strong>Virtualbox 5.1.18</strong>. I get the following error message:</p>
  
  <blockquote>
    <p>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:</p>
  
  <pre><code> mount -t vboxsf -o uid=1000,gid=1000 keys /keys 
  </code></pre>
    
    <p>The error output from the command was:</p>
  
  <pre><code>mount: wrong fs type, bad option, bad superblock on keys,
  missing codepage or helper program, or other error
  In some cases useful info is found in syslog - try dmesg | tail or so.
  </code></pre>
  </blockquote>
  
  <p>I have tried manually installing <code>vagrant-vbguest</code> plugin (via <code>vagrant plugin install vagrant-vbguest</code>), but that fixed nothing. Downgrading back to 5.1.18 does resolve it, but this isn't ideal moving forward.</p>
  
  <p>How can I get folder mounting working with <strong>Virtualbox 5.1.20</strong> and <strong>Vagrant 1.9.3</strong>?</p>