Specifying an instance type or preference - Virtual machines | Virtualization

Using flags to specify instance types and preferences
Inferring an instance type or preference
Setting the inferFromVolume labels

You can specify an instance type, a preference, or both to define a set of workload sizing and runtime characteristics for reuse across multiple VMs.

Using flags to specify instance types and preferences

Specify instance types and preferences by using flags.

Prerequisites

You must have an instance type, preference, or both on the cluster.

Procedure

To specify an instance type when creating a VM, use the --instancetype flag. To specify a preference, use the --preference flag. The following example includes both flags:
```
$ virtctl create vm --instancetype <my_instancetype> --preference <my_preference>
```
Optional: To specify a namespaced instance type or preference, include the kind in the value passed to the --instancetype or --preference flag command. The namespaced instance type or preference must be in the same namespace you are creating the VM in. The following example includes flags for a namespaced instance type and a namespaced preference:
```
$ virtctl create vm --instancetype virtualmachineinstancetype/<my_instancetype> --preference virtualmachinepreference/<my_preference>
```

Inferring an instance type or preference

Inferring instance types, preferences, or both is enabled by default, and the inferFromVolumeFailure policy of the inferFromVolume attribute is set to Ignore. When inferring from the boot volume, errors are ignored, and the VM is created with the instance type and preference left unset.

However, when flags are applied, the inferFromVolumeFailure policy defaults to Reject. When inferring from the boot volume, errors result in the rejection of the creation of that VM.

You can use the --infer-instancetype and --infer-preference flags to infer which instance type, preference, or both to use to define the workload sizing and runtime characteristics of a VM.

Prerequisites

You have installed the virtctl tool.

Procedure

To explicitly infer instance types from the volume used to boot the virtual machine, use the --infer-instancetype flag. To explicitly infer preferences, use the --infer-preference flag. The following command includes both flags:
```
$ virtctl create vm --volume-import type:pvc,src:my-ns/my-pvc --infer-instancetype --infer-preference
```

Setting the inferFromVolume labels

Use the following labels on your PVC, data source, or data volume to instruct the inference mechanism which instance type, preference, or both to use when trying to boot from a volume.

A cluster-wide instance type: instancetype.kubevirt.io/default-instancetype label.
A namespaced instance type: instancetype.kubevirt.io/default-instancetype-kind label. Defaults to the VirtualMachineClusterInstancetype label if left empty.
A cluster-wide preference: instancetype.kubevirt.io/default-preference label.
A namespaced preference: instancetype.kubevirt.io/default-preference-kind label. Defaults to VirtualMachineClusterPreference label, if left empty.

Prerequisites

You must have an instance type, preference, or both on the cluster.

Procedure

To apply a label to a data source, use oc label. The following command applies a label that points to a cluster-wide instance type:
```
$ oc label DataSource foo instancetype.kubevirt.io/default-instancetype=<my_instancetype>
```