I'd like to install GuixSD in a vm made with Boxes on Fedora 28 x86_64

There's an ISO imagge for installing GuixSD but the porcess is lengthy, so I shut the vm down with the idea of continuing later

Boxes atomatically erased my vm and I had to "undo" that

Why is that ? What's the assumption in erasing a vm that has been switched off ?

Also, After the shutdown, the vm won't boot anymore

It tries to boot from the hard drive instead of the cd-rom (the iso image)

So I should complete the GuixSD installation process in a single session

But I want to break the session in parts !

How can I achieve that ?