Check usability of nfs on host

lib/vagrant/errors.rb

@@ -460,6 +460,10 @@ module Vagrant
       error_key(:nfs_no_valid_ids)
     end
 
+    class NFSNotSupported < VagrantError
+      error_key(:nfs_not_supported)
+    end
+
     class NFSClientNotInstalledInGuest < VagrantError
       error_key(:nfs_client_not_installed_in_guest)
     end

plugins/synced_folders/nfs/synced_folder.rb

@@ -30,14 +30,9 @@ module VagrantPlugins
         if !machine.config.nfs.functional
           return false
         end
-
-        # We don't currently support NFS on Windows
-        if Vagrant::Util::Platform.windows?
-          return false
-        end
-
-        # NFS is always available
-        true
+        return true if machine.env.host.capability(:nfs_installed)
+        return false if !raise_error
+        raise Vagrant::Errors::NFSNotSupported
       end
 
       def prepare(machine, folders, opts)

templates/locales/en.yml

@@ -813,6 +813,12 @@ en:
         No valid IDs were given to the NFS synced folder implementation to
         prune. This is an internal bug with Vagrant and an issue should be
         filed.
+      nfs_not_supported: |-
+        It appears your machine doesn't support NFS, or there is not an
+        adapter to enable NFS on this machine for Vagrant. Please verify
+        that `nfsd` is installed on your machine, and try again. If you're
+        on Windows, NFS isn't supported. If the problem persists, please
+        contact Vagrant support.
       nfs_client_not_installed_in_guest: |-
         No NFS client was detected as installed in your guest machine. This
         is required for NFS synced folders to work. In addition to this, Vagrant