add box的時候默認保存在 C:\Users\xxx\.vagrant.d
VAGRANT_HOME can be set to change the directory where Vagrant stores global state. By default, this is set to ~/.vagrant.d. The Vagrant home directory is where things such as boxes are stored, so it can actually become quite large on disk.
通過設置VAGRANT_HOME環境變量改變默認位置
setx VAGRANT_HOME "X:/your/path"
setx VAGRANT_HOME "X:/your/path" /M （系統變量）