ubuntu 16.04 install windows 7 virtual machine

1. install virtualbox
   sudo apt-get install virtualbox

2. Install Windows using IOS files.
   (1) You can customize the allocated hard disk size under the advanced options.
   (2) After the operating environment is established, put the IOS file into the simulated driver disk, and click Start to customize the installation.

3. Add a shared folder
   (1) Open the Windows 7 system, click the top menu of Virtualbox, Device -> Install Enhancements, and install it.
   (2) Click Device -> Shared Folder, add a shared path, and set it as a fixed allocation.
   (3) In the Windows 7 network, you can search for shared folders.

4. Virtualbox supports USB devices
   (1) Add usbfs user group (there will be vboxusers and vboxsf after virtualbox is installed)
   sudo groupadd usbfs
   (2) Add your common Linux users to the two groups of vboxusers and usbfs

   sudo adduser carl vboxusers
   sudo adduser carl usbfs

(3) Restart the computer