Now checks for VirtualBox installation and proper version and gives sensible error if not detected.

Gemfile

@@ -1,7 +1,7 @@
 source :gemcutter
 
 # Gems required for the lib to even run
-gem "virtualbox", ">= 0.5.0"
+gem "virtualbox", ">= 0.5.1"
 gem "net-ssh", ">= 2.0.19"
 gem "net-scp", ">= 1.0.2"
 gem "git-style-binaries", ">= 0.1.10"

Rakefile

@@ -10,7 +10,7 @@ begin
     gemspec.homepage = "http://github.com/mitchellh/vagrant"
     gemspec.authors = ["Mitchell Hashimoto", "John Bender"]
 
-    gemspec.add_dependency('virtualbox', '>= 0.5.0')
+    gemspec.add_dependency('virtualbox', '>= 0.5.1')
     gemspec.add_dependency('net-ssh', '>= 2.0.19')
     gemspec.add_dependency('net-scp', '>= 1.0.2')
     gemspec.add_dependency('json', '>= 1.2.0')

lib/vagrant/env.rb

@@ -24,9 +24,36 @@ module Vagrant
         load_config!
         load_home_directory!
         load_box!
+        check_virtualbox!
         load_vm!
       end
 
+      def check_virtualbox!
+        version = VirtualBox::Command.version
+        if version.nil?
+          error_and_exit(<<-msg)
+Vagrant could not detect VirtualBox! Make sure VirtualBox is properly installed.
+If VirtualBox is installed, you may need to tweak the paths to the `VBoxManage`
+application which ships with VirtualBox and the path to the global XML configuration
+which VirtualBox typically stores somewhere in your home directory.
+
+The following shows how to configure VirtualBox. This can be done in the
+Vagrantfile. Note that 90% of the time, you shouldn't need to do this if VirtualBox
+is installed. Please use the various Vagrant support lines to request more information
+if you can't get this working.
+
+VirtualBox::Command.vboxmanage = "/path/to/my/VBoxManage"
+VirtualBox::Global.vboxconfig = "~/path/to/VirtualBox.xml"
+msg
+        elsif version.to_f < 3.0
+          error_and_exit(<<-msg)
+Vagrant has detected that you have VirtualBox version #{version} installed!
+Vagrant requires that you use at least VirtualBox version 3. Please install
+a more recent version of VirtualBox to continue.
+msg
+        end
+      end
+
       def load_config!
         # Prepare load paths for config files
         load_paths = [File.join(PROJECT_ROOT, "config", "default.rb")]

test/vagrant/env_test.rb

@@ -15,6 +15,24 @@ class EnvTest < Test::Unit::TestCase
     Vagrant::Box.stubs(:find).returns("foo")
   end
 
+  context "checking virtualbox version" do
+    setup do
+      VirtualBox::Command.stubs(:version)
+    end
+
+    should "error and exit if VirtualBox is not installed or detected" do
+      Vagrant::Env.expects(:error_and_exit).once
+      VirtualBox::Command.expects(:version).returns(nil)
+      Vagrant::Env.check_virtualbox!
+    end
+
+    should "error and exit if VirtualBox is lower than version 3" do
+      Vagrant::Env.expects(:error_and_exit).once
+      VirtualBox::Command.expects(:version).returns("2.1.3r1041")
+      Vagrant::Env.check_virtualbox!
+    end
+  end
+
   context "requiring a VM" do
     setup do
       Vagrant::Env.stubs(:require_root_path)
@@ -130,11 +148,13 @@ class EnvTest < Test::Unit::TestCase
 
   context "initial load" do
     test "load! should load the config and set the persisted_uid" do
-      Vagrant::Env.expects(:load_config!).once
-      Vagrant::Env.expects(:load_vm!).once
-      Vagrant::Env.expects(:load_root_path!).once
-      Vagrant::Env.expects(:load_home_directory!).once
-      Vagrant::Env.expects(:load_box!).once
+      call_seq = sequence("call_sequence")
+      Vagrant::Env.expects(:load_root_path!).once.in_sequence(call_seq)
+      Vagrant::Env.expects(:load_config!).once.in_sequence(call_seq)
+      Vagrant::Env.expects(:load_home_directory!).once.in_sequence(call_seq)
+      Vagrant::Env.expects(:load_box!).once.in_sequence(call_seq)
+      Vagrant::Env.expects(:check_virtualbox!).once.in_sequence(call_seq)
+      Vagrant::Env.expects(:load_vm!).once.in_sequence(call_seq)
       Vagrant::Env.load!
     end
   end

vagrant.gemspec

@@ -156,14 +156,14 @@ Gem::Specification.new do |s|
     s.specification_version = 3
 
     if Gem::Version.new(Gem::RubyGemsVersion) >= Gem::Version.new('1.2.0') then
-      s.add_runtime_dependency(%q<virtualbox>, [">= 0.5.0"])
+      s.add_runtime_dependency(%q<virtualbox>, [">= 0.5.1"])
       s.add_runtime_dependency(%q<net-ssh>, [">= 2.0.19"])
       s.add_runtime_dependency(%q<net-scp>, [">= 1.0.2"])
       s.add_runtime_dependency(%q<json>, [">= 1.2.0"])
       s.add_runtime_dependency(%q<git-style-binaries>, [">= 0.1.10"])
       s.add_runtime_dependency(%q<archive-tar-minitar>, ["= 0.5.2"])
     else
-      s.add_dependency(%q<virtualbox>, [">= 0.5.0"])
+      s.add_dependency(%q<virtualbox>, [">= 0.5.1"])
       s.add_dependency(%q<net-ssh>, [">= 2.0.19"])
       s.add_dependency(%q<net-scp>, [">= 1.0.2"])
       s.add_dependency(%q<json>, [">= 1.2.0"])
@@ -171,7 +171,7 @@ Gem::Specification.new do |s|
       s.add_dependency(%q<archive-tar-minitar>, ["= 0.5.2"])
     end
   else
-    s.add_dependency(%q<virtualbox>, [">= 0.5.0"])
+    s.add_dependency(%q<virtualbox>, [">= 0.5.1"])
     s.add_dependency(%q<net-ssh>, [">= 2.0.19"])
     s.add_dependency(%q<net-scp>, [">= 1.0.2"])
     s.add_dependency(%q<json>, [">= 1.2.0"])