Vagrant error : Failed to mount folders in Linux guest

The plugin vagrant-vbguest solved my problem:

$ vagrant plugin install vagrant-vbguest

Output:

$ vagrant reload
==> default: Attempting graceful shutdown of VM...
...
==> default: Machine booted and ready!
GuestAdditions 4.3.12 running --- OK.
==> default: Checking for guest additions in VM...
==> default: Configuring and enabling network interfaces...
==> default: Exporting NFS shared folders...
==> default: Preparing to edit /etc/exports. Administrator privileges will be required...
==> default: Mounting NFS shared folders...
==> default: VM already provisioned. Run `vagrant provision` or use `--provision` to force it

Just make sure you are running the latest version of VirtualBox

I found this issue addressed here vagrant issues. Two ways to do it:

1. Run this on guest (i.e. after you ssh into vbox via vagrant ssh )

   sudo ln -s /opt/VBoxGuestAdditions-4.3.10/lib/VBoxGuestAdditions /usr/lib/VBoxGuestAdditions
   

   Then run vagrant reload to correctly mount the folders.

2. As @klang pointed out, update the VBoxGuestAdditions.iso file on your mac:

   wget https://www.virtualbox.org/download/testcase/VBoxGuestAdditions_4.3.11-93070.iso‌​
   sudo cp VBoxGuestAdditions_4.3.11-93070.iso /Applications/VirtualBox.app/Contents/MacOS/VBoxGuestAdditions.iso
   

UPDATE (16may2014)

Since the iso is no longer available, you can use the 4.3.12 one (http://dlc.sun.com.edgesuite.net/virtualbox/4.3.12/VBoxGuestAdditions_4.3.12.iso)

note : the binary vbox4.3.12 for os X is not available at this time