Creating virtual machines from the command line - Advanced VM creation | Virtualization

Creating a VM from a VirtualMachine manifest
- Supported custom video device types

You can create virtual machines (VMs) from the command line by editing or creating a VirtualMachine manifest. You can simplify VM configuration by using an instance type in your VM manifest.

You can also create VMs from instance types by using the web console.

Creating a VM from a VirtualMachine manifest

You can create a virtual machine (VM) from a VirtualMachine manifest. To simplify the creation of these manifests, you can use the virtctl command-line tool.

Prerequisites

You have installed the virtctl CLI.
You have installed the OpenShift CLI (oc).

Procedure

Create a VirtualMachine manifest for your VM and save it as a YAML file. For example, to create a minimal Fedora VM, run the following command:
```
$ virtctl create vm --name rhel-9-minimal --volume-import type:ds,src:openshift-virtualization-os-images/rhel9
```

Review the VirtualMachine manifest for your VM:

This example manifest does not configure VM authentication.

Example manifest for a Fedora VM

apiVersion: kubevirt.io/v1
kind: VirtualMachine
metadata:
  name: rhel-9-minimal
spec:
  dataVolumeTemplates:
  - metadata:
      name: imported-volume-mk4lj
    spec:
      sourceRef:
        kind: DataSource
        name: rhel9
        namespace: openshift-virtualization-os-images
      storage:
        resources: {}
  instancetype:
    inferFromVolume: imported-volume-mk4lj
    inferFromVolumeFailurePolicy: Ignore
  preference:
    inferFromVolume: imported-volume-mk4lj
    inferFromVolumeFailurePolicy: Ignore
  runStrategy: Always
  template:
    spec:
      domain:
        devices:
          video:
            type: virtio
        memory:
          guest: 512Mi
        resources: {}
      terminationGracePeriodSeconds: 180
      volumes:
      - dataVolume:
          name: imported-volume-mk4lj
        name: imported-volume-mk4lj

name: rhel-9-minimal specifies the name of the VM.
name: rhel9 specifies the boot source for the guest operating system in the sourceRef section.
namespace: openshift-virtualization-os-images specifies the namespace for the boot source. Golden images are stored in the openshift-virtualization-os-images namespace.
instancetype: inferFromVolume: imported-volume-mk4lj specifies the instance type inferred from the selected DataSource object.
preference: inferFromVolume: imported-volume-mk4lj specifies that the preference is inferred from the selected DataSource object.
type: virtio specifies the use of a custom video device (a VirtIO device in this example) to enable hardware graphics acceleration. Enabling a custom video device is in Technology Preview for OKD Virtualization 4.21.

Create a virtual machine by using the manifest file:
```
$ oc create -f <vm_manifest_file>.yaml
```
Optional: Start the virtual machine:
```
$ virtctl start <vm_name>
```

Supported custom video device types

When creating a virtual machine (VM), you can configure a custom video device type to override the default video configuration.

Configuring a custom video device allows you to specify different video devices, based on your guest operating system requirements and performance needs.

Custom video device support is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.

For more information about the support scope of Red Hat Technology Preview features, see Technology Preview Features Support Scope.

Using a custom video device provides several advantages:

Performance: Certain video devices provide better performance than the default configuration. For example, VirtIO is a more efficient video device on AMD/x86_64 architecture than legacy VGA.
Resolution flexibility: With some video device types, you can set custom display resolutions.
Memory efficiency: Some video types are more memory efficient for headless or console-only operations.

You can configure the following video device types:

VirtIO: provides improved performance, and hardware-accelerated video decoding and encoding by offloading tasks to the host. Recommended for modern guest operating systems with available VirtIO drivers.
VGA: the standard for analog video display (default on AMD/x86_64 with BIOS).
Bochs: an emulated graphics adapter that provides a simple interface for guest operating systems to manage display settings (default on AMD/x86_64 with EFI).
Cirrus: a legacy video device that provides stable video output.
ramfb: a simple, unaccelerated virtual display device primarily used in the QEMU emulator, and useful for ARM architecture.

Table 1. Video device support by architecture
Architecture	Boot mode	Default type	Supported types
AMD/x86_64	BIOS	`vga`	`virtio`, `vga`, `bochs`, `cirrus`, ramfb`
AMD/x86_64	EFI	`bochs`	`virtio`, `vga`, `bochs`, `cirrus`, ramfb`
ARM64	BIOS/EFI	`virtio`	`virtio`, `ramfb`
s390x	BIOS/EFI	`virtio`	`virtio`

Next steps

Configuring SSH access to virtual machines

Creating virtual machines from the CLI

Creating a VM from a VirtualMachine manifest

Supported custom video device types