A Vagrant plugin to add a disks in VirtualBox
vagrant plugin install vagrant-newdisk
Set the size you want for your disk in your Vagrantfile. For example
Vagrant.configure('2') do |config|
config.vm.box = 'ubuntu/xenial64'
config.newdisk.size = 10 * 1024 # size in megabytes
config.newdisk.path = "/tmp/your-file.vdi"
end
At present only one disk can be added to the first controller.
The gem is available as open source under the terms of the MIT License.