Helpful error message if NFS mount fails in Linux [closes GH-135]

CHANGELOG.md

@@ -16,6 +16,7 @@
   - Removed check and error for the "OSE" version of VirtualBox, since with
     VirtualBox 4 this distinction no longer exists.
   - Ability to specify proxy settings for chef. [GH-169]
+  - Helpful error message shown if NFS mounting fails. [GH-135]
 
 ## 0.7.0.beta (December 24, 2010)
 

lib/vagrant/systems/linux.rb

@@ -57,7 +57,7 @@ module Vagrant
         folders.each do |name, opts|
           vm.ssh.execute do |ssh|
             ssh.exec!("sudo mkdir -p #{opts[:guestpath]}")
-            ssh.exec!("sudo mount #{ip}:#{opts[:hostpath]} #{opts[:guestpath]}")
+            ssh.exec!("sudo mount #{ip}:#{opts[:hostpath]} #{opts[:guestpath]}", :error_class => LinuxError, :_key => :mount_nfs_fail)
           end
         end
       end

templates/locales/en.yml

@@ -463,6 +463,12 @@ en:
       linux:
         attempting_halt: "Attempting graceful shutdown of linux..."
         mount_fail: "Failed to mount shared folders. `vboxsf` was not available."
+        mount_nfs_fail: |-
+          Mounting NFS shared folders failed. This is most often caused by the NFS
+          client software not being installed on the guest machine. Please verify
+          that the NFS client software is properly installed, and consult any resources
+          specific to the linux distro you're using for more information on how to
+          do this.
         network_not_debian: |-
           Host only networking is only supported for Debian/Ubuntu by the built-in
           "Linux" system. If you're using some other distro and want to implement