任何插件的运行vagrant plugin install [plugin]都失败（使用管理员命令提示符）。不确定是什么问题。dev/null不在我的机器上，它不应该尝试安装到 VM。
试过：
- 卸载 Vagrant，删除
.vagrant.d目录，重新安装 Vagrant - 使用嵌入的 Ruby 更新 Vagrant 的 gem
- 更新 VirtualBox
- 禁用 .bashrc 文件（也用 Git Bash 尝试过）
使用：
- Windows 7 专业版 x64 SP1
- 流浪者 1.7.2
- 虚拟盒子 4.3.26
输出：
注意：**=C:/HashiCorp/Vagrant/embedded
C:\Users\Joe\Dropbox\webdev\projects>vagrant plugin install vagrant-hostsupdater
Installing the 'vagrant-hostsupdater' plugin. This can take a few minutes...
**/lib/ruby/2.0.0/rubygems/user_interaction.rb:554:in \`initialize':
Is a directory - /dev/null (Errno::EISDIR)
from **/lib/ruby/2.0.0/rubygems/user_interaction.rb:554:in \`open'
from **/lib/ruby/2.0.0/rubygems/user_interaction.rb:554:in \`initialize'
from **/gems/gems/vagrant-1.7.2/lib/vagrant/bundler.rb:283:in \`new'
from **/gems/gems/vagrant-1.7.2/lib/vagrant/bundler.rb:283:in \`with_isolated_gem'
from **/gems/gems/vagrant-1.7.2/lib/vagrant/bundler.rb:225:in \`internal_install'
from **/gems/gems/vagrant-1.7.2/lib/vagrant/bundler.rb:92:in \`install'
from **/gems/gems/vagrant-1.7.2/lib/vagrant/plugin/manager.rb:62:in \`block in install_plugin'
from **/gems/gems/vagrant-1.7.2/lib/vagrant/plugin/manager.rb:72:in \`call'
from **/gems/gems/vagrant-1.7.2/lib/vagrant/plugin/manager.rb:72:in \`install_plugin'
from **/gems/gems/vagrant-1.7.2/plugins/commands/plugin/action/install_gem.rb:37:in \`call'
from **/gems/gems/vagrant-1.7.2/lib/vagrant/action/warden.rb:34:in \`call'
from **/gems/gems/vagrant-1.7.2/lib/vagrant/action/builder.rb:116:in \`call'
from **/gems/gems/vagrant-1.7.2/lib/vagrant/action/runner.rb:66:in \`block in run'
from **/gems/gems/vagrant-1.7.2/lib/vagrant/util/busy.rb:19:in \`busy'
from **/gems/gems/vagrant-1.7.2/lib/vagrant/action/runner.rb:66:in \`run'
from **/gems/gems/vagrant-1.7.2/plugins/commands/plugin/command/base.rb:14:in \`action'
from **/gems/gems/vagrant-1.7.2/plugins/commands/plugin/command/install.rb:32:in \`block in execute'
from **/gems/gems/vagrant-1.7.2/plugins/commands/plugin/command/install.rb:31:in \`each'
from **/gems/gems/vagrant-1.7.2/plugins/commands/plugin/command/install.rb:31:in \`execute'
from **/gems/gems/vagrant-1.7.2/plugins/commands/plugin/command/root.rb:56:in \`execute'
from **/gems/gems/vagrant-1.7.2/lib/vagrant/cli.rb:42:in \`execute'
from **/gems/gems/vagrant-1.7.2/lib/vagrant/environment.rb:301:in \`cli'
from **/gems/gems/vagrant-1.7.2/bin/vagrant:174:in \`<main>'