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Using UEFI mode for virtual machines

You can boot a virtual machine (VM) in Unified Extensible Firmware Interface (UEFI) mode for faster boot times, the ability to boot to larger disks, and added security features.

About UEFI mode for virtual machines

Unified Extensible Firmware Interface (UEFI), like legacy BIOS, initializes hardware components and operating system image files when a computer starts. UEFI supports more modern features and customization options than BIOS, enabling faster boot times.

It stores all the information about initialization and startup in a file with a .efi extension, which is stored on a special partition called EFI System Partition (ESP). The ESP also contains the boot loader programs for the operating system that is installed on the computer.

Booting virtual machines in UEFI mode

You can configure a virtual machine to boot in UEFI mode by editing the VirtualMachine manifest.

Prerequisites

  • Install the OpenShift CLI (oc).

Procedure

  1. Edit or create a VirtualMachine manifest file. Use the spec.firmware.bootloader stanza to configure UEFI mode.

    Booting in UEFI mode with secure boot active:

apiversion: kubevirt.io/v1
kind: VirtualMachine
metadata:
  labels:
    special: vm-secureboot
  name: vm-secureboot
spec:
  template:
    metadata:
      labels:
        special: vm-secureboot
    spec:
      domain:
        devices:
          disks:
          - disk:
              bus: virtio
            name: containerdisk
        features:
          acpi: {}
          smm:
            enabled: true
        firmware:
          bootloader:
            efi:
              secureBoot: true
# ...

+ * You must set spec.template.spec.domain.features.ssm.enabled to have a value of true. * If spec.template.spec.domain.firmware.bootloader.efi.secureBoot is set to true, then UEFI mode is required. However, you can enable UEFI mode without using Secure Boot.

  1. Apply the manifest to your cluster by running the following command:

    $ oc create -f <file_name>.yaml

Enabling persistent EFI

You can enable EFI persistence in a VM by configuring an RWX storage class at the cluster level and adjusting the settings in the EFI section of the VM.

Prerequisites

  • You must have cluster administrator privileges.

  • You must have a storage class that supports RWX access mode and FS volume mode.

  • You have installed the OpenShift CLI (oc).

Procedure

  • Enable the VMPersistentState feature gate by running the following command:

    $ oc patch hyperconverged kubevirt-hyperconverged -n kubevirt-hyperconverged \
  --type json -p '[{"op":"replace","path":"/spec/featureGates/VMPersistentState", "value": true}]'

Configuring VMs with persistent EFI

You can configure a VM to have EFI persistence enabled by editing its manifest file.

Prerequisites

  • VMPersistentState feature gate enabled.

Procedure

  • Edit the VM manifest file and save to apply settings.

    apiVersion: kubevirt.io/v1
kind: VirtualMachine
metadata:
  name: vm
spec:
  template:
    spec:
      domain:
        firmware:
          bootloader:
            efi:
              persistent: true
# ...