Creating VMs from templates - Virtual machines | Virtualization

About VM templates
Creating a VM from a template

You can create virtual machines (VMs) from Red Hat templates by using the OKD web console.

About VM templates

Boot sources: You can expedite VM creation by using templates that have an available boot source. Templates with a boot source are labeled Available boot source if they do not have a custom label.

Templates without a boot source are labeled Boot source required. See Creating virtual machines from custom images.
Customization: You can customize the disk source and VM parameters before you start the VM.

See storage volume types and storage fields for details about disk source settings.

If you copy a VM template with all its labels and annotations, your version of the template is marked as deprecated when a new version of the Scheduling, Scale, and Performance (SSP) Operator is deployed. You can remove this designation. See Customizing a VM template by using the web console.

Single-node OpenShift: Due to differences in storage behavior, some templates are incompatible with single-node OpenShift. To ensure compatibility, do not set the evictionStrategy field for templates or VMs that use data volumes or storage profiles.

Creating a VM from a template

You can create a virtual machine (VM) from a template with an available boot source by using the OKD web console.

Optional: You can customize template or VM parameters, such as data sources, cloud-init, or SSH keys, before you start the VM.

Procedure

Navigate to Virtualization → Catalog in the web console.
Click Boot source available to filter templates with boot sources.

The catalog displays the default templates. Click All Items to view all available templates for your filters.
Click a template tile to view its details.
Optional: If you are using a Windows template, you can mount a Windows driver disk by selecting the Mount Windows drivers disk checkbox.
If you do not need to customize the template or VM parameters, click Quick create VirtualMachine to create a VM from the template.

If you need to customize the template or VM parameters, do the following:
1. Click Customize VirtualMachine.
2. Expand Storage or Optional parameters to edit data source settings.
3. Click Customize VirtualMachine parameters.
  
  The Customize and create VirtualMachine pane displays the Overview, YAML, Scheduling, Environment, Network interfaces, Disks, Scripts, and Metadata tabs.
4. Edit the parameters that must be set before the VM boots, such as cloud-init or a static SSH key.
5. Click Create VirtualMachine.
  
  The VirtualMachine details page displays the provisioning status.

Storage volume types

Type Description

ephemeral

A local copy-on-write (COW) image that uses a network volume as a read-only backing store. The backing volume must be a PersistentVolumeClaim. The ephemeral image is created when the virtual machine starts and stores all writes locally. The ephemeral image is discarded when the virtual machine is stopped, restarted, or deleted. The backing volume (PVC) is not mutated in any way.

persistentVolumeClaim

Attaches an available PV to a virtual machine. Attaching a PV allows for the virtual machine data to persist between sessions.

Importing an existing virtual machine disk into a PVC by using CDI and attaching the PVC to a virtual machine instance is the recommended method for importing existing virtual machines into OKD. There are some requirements for the disk to be used within a PVC.

dataVolume

Data volumes build on the persistentVolumeClaim disk type by managing the process of preparing the virtual machine disk via an import, clone, or upload operation. VMs that use this volume type are guaranteed not to start until the volume is ready.

Specify type: dataVolume or type: "". If you specify any other value for type, such as persistentVolumeClaim, a warning is displayed, and the virtual machine does not start.

cloudInitNoCloud

Attaches a disk that contains the referenced cloud-init NoCloud data source, providing user data and metadata to the virtual machine. A cloud-init installation is required inside the virtual machine disk.

containerDisk

References an image, such as a virtual machine disk, that is stored in the container image registry. The image is pulled from the registry and attached to the virtual machine as a disk when the virtual machine is launched.

A containerDisk volume is not limited to a single virtual machine and is useful for creating large numbers of virtual machine clones that do not require persistent storage.

Only RAW and QCOW2 formats are supported disk types for the container image registry. QCOW2 is recommended for reduced image size.

A containerDisk volume is ephemeral. It is discarded when the virtual machine is stopped, restarted, or deleted. A containerDisk volume is useful for read-only file systems such as CD-ROMs or for disposable virtual machines.

emptyDisk

Creates an additional sparse QCOW2 disk that is tied to the life-cycle of the virtual machine interface. The data survives guest-initiated reboots in the virtual machine but is discarded when the virtual machine stops or is restarted from the web console. The empty disk is used to store application dependencies and data that otherwise exceeds the limited temporary file system of an ephemeral disk.

The disk capacity size must also be provided.

Storage fields

Field Description

Field	Description
Blank (creates PVC)	Create an empty disk.
Import via URL (creates PVC)	Import content via URL (HTTP or HTTPS endpoint).
Use an existing PVC	Use a PVC that is already available in the cluster.
Clone existing PVC (creates PVC)	Select an existing PVC available in the cluster and clone it.
Import via Registry (creates PVC)	Import content via container registry.
Container (ephemeral)	Upload content from a container located in a registry accessible from the cluster. The container disk should be used only for read-only filesystems such as CD-ROMs or temporary virtual machines.
Name	Name of the disk. The name can contain lowercase letters (`a-z`), numbers (`0-9`), hyphens (`-`), and periods (`.`), up to a maximum of 253 characters. The first and last characters must be alphanumeric. The name must not contain uppercase letters, spaces, or special characters.
Size	Size of the disk in GiB.
Type	Type of disk. Example: Disk or CD-ROM
Interface	Type of disk device. Supported interfaces are virtIO, SATA, and SCSI.
Storage Class	The storage class that is used to create the disk.

Blank (creates PVC)

Create an empty disk.

Import via URL (creates PVC)

Import content via URL (HTTP or HTTPS endpoint).

Use an existing PVC

Use a PVC that is already available in the cluster.

Clone existing PVC (creates PVC)

Select an existing PVC available in the cluster and clone it.

Import via Registry (creates PVC)

Import content via container registry.

Container (ephemeral)

Upload content from a container located in a registry accessible from the cluster. The container disk should be used only for read-only filesystems such as CD-ROMs or temporary virtual machines.

Name

Name of the disk. The name can contain lowercase letters (a-z), numbers (0-9), hyphens (-), and periods (.), up to a maximum of 253 characters. The first and last characters must be alphanumeric. The name must not contain uppercase letters, spaces, or special characters.

Size

Size of the disk in GiB.

Type

Type of disk. Example: Disk or CD-ROM

Interface

Type of disk device. Supported interfaces are virtIO, SATA, and SCSI.

Storage Class

The storage class that is used to create the disk.

Advanced storage settings

The following advanced storage settings are optional and available for Blank, Import via URL, and Clone existing PVC disks.

If you do not specify these parameters, the system uses the default storage profile values.

Parameter Option Parameter description

Volume Mode

Filesystem

Stores the virtual disk on a file system-based volume.

Block

Stores the virtual disk directly on the block volume. Only use Block if the underlying storage supports it.

Access Mode

ReadWriteOnce (RWO)

Volume can be mounted as read-write by a single node.

ReadWriteMany (RWX)

Volume can be mounted as read-write by many nodes at one time.

This mode is required for live migration.

Customizing a VM template by using the web console

You can customize an existing virtual machine (VM) template by modifying the VM or template parameters, such as data sources, cloud-init, or SSH keys, before you start the VM. If you customize a template by copying it and including all of its labels and annotations, the customized template is marked as deprecated when a new version of the Scheduling, Scale, and Performance (SSP) Operator is deployed.

You can remove the deprecated designation from the customized template.