Enhancement Request: Add `vagrant define` subcommand

[Wenzel]

Feature Request: Add vagrant define Subcommand

Is your feature request related to a problem? Please describe.

Currently, when using vagrant-libvirt, Vagrant automatically creates and starts a domain upon running vagrant up. However, in certain scenarios, users may want to only define the domain without starting it. One specific use case is when a user wants to take a snapshot of the VM in an untouched state before its first boot.

This limitation makes it difficult to:

• Create snapshots before first boot (useful for forensic analysis, golden images, etc.).
• Inspect or modify the libvirt domain XML before execution.
• Set up multi-VM configurations where some machines should not start immediately.

Describe the solution you'd like

Introduce a new subcommand:

vagrant define

This command would behave similarly to vagrant up, but instead of booting the VM, it would only define the domain in libvirt. This allows:

• Creating a libvirt domain from Vagrant’s configuration.
• Using standard libvirt tooling (e.g., virsh snapshot-create-as) to take an untouched snapshot before the VM runs.
• Further manual modifications to the VM definition before starting.

Behavior:

• Runs the provisioning pipeline up to the point of defining the domain, then stops.
• Does not boot the VM.
• The next vagrant up would recognize that the domain is already defined and proceed with normal startup.

Describe alternatives you've considered

No real alternatives as vagrant up with vagrant-libvirt creates the libvirt XML and the VM in one go

Would love to hear feedback from maintainers and the community on whether this feature would be a good addition to Vagrant.