Когда вы запустите vmbuilder <hypervisor> ubuntu --help, выведите страницу справки, в которой я читаю
--iso=PATH Use an iso image as the source for installation of file. Full path to the iso must be provided. If --mirror is also provided, it
will be used in the final sources.list of the vm. This requires suite and kernel parameter to match what is available on the iso,
obviously.
Я не пробовал это.