VirtualBoxが入っていなかったので，インストールした．

# VirtualBoxが入っていなかったので，インストールした．

$ vg up
> ... (中略)
> If you believe you already have a provider available, make sure it
> is properly installed and configured. You can see more details about
> why a particular provider isn't working by forcing usage with
> `vagrant up --provider=PROVIDER`, which should give you a more specific
> error message for that particular provider.

$ virtualbox
> -bash: virtualbox: command not found

# VirtualBoxをサイト(https://www.virtualbox.org/wiki/Downloads)からダウンロードする．

$ vagrant up
> ... (省略)