7.11. Advanced virtual machine management

Procedure

1. Edit an Ansible Playbook YAML file so that it includes the kubevirt_vm task:

     kubevirt_vm:
       namespace:
       name:
       cpu_cores:
       memory:
       disks:
         - name:
           volume:
             containerDisk:
               image:
           disk:
             bus:

   注意

   This snippet only includes the kubevirt_vm portion of the playbook.

2. Edit the values to reflect the virtual machine you want to create, including the namespace, the number of cpu_cores, the memory, and the disks. For example:

     kubevirt_vm:
       namespace: default
       name: vm1
       cpu_cores: 1
       memory: 64Mi
       disks:
         - name: containerdisk
           volume:
             containerDisk:
               image: kubevirt/cirros-container-disk-demo:latest
           disk:
             bus: virtio

3. If you want the virtual machine to boot immediately after creation, add state: running to the YAML file. For example:

     kubevirt_vm:
       namespace: default
       name: vm1
       state: running 1
       cpu_cores: 1

   1

   Changing this value to state: absent deletes the virtual machine, if it already exists.

4. Run the ansible-playbook command, using your playbook’s file name as the only argument:

   $ ansible-playbook create-vm.yaml

5. Review the output to determine if the play was successful:

   Example output

   (...)
   TASK [Create my first VM] ************************************************************************
   changed: [localhost]
   
   PLAY RECAP ********************************************************************************************************
   localhost                  : ok=2    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

6. If you did not include state: running in your playbook file and you want to boot the VM now, edit the file so that it includes state: running and run the playbook again:

   $ ansible-playbook create-vm.yaml

Procedure

1. Configure a PXE network on the cluster:

   1. Create the NetworkAttachmentDefinition file for PXE network pxe-net-conf:

      apiVersion: "k8s.cni.cncf.io/v1"
      kind: NetworkAttachmentDefinition
      metadata:
        name: pxe-net-conf
      spec:
        config: '{
          "cniVersion": "0.3.1",
          "name": "pxe-net-conf",
          "plugins": [
            {
              "type": "cnv-bridge",
              "bridge": "br1",
              "vlan": 1 1
            },
            {
              "type": "cnv-tuning" 2
            }
          ]
        }'

      1

      Optional: The VLAN tag.

      2

      The cnv-tuning plug-in provides support for custom MAC addresses.

      注意

      The virtual machine instance will be attached to the bridge br1 through an access port with the requested VLAN.

2. Create the NetworkAttachmentDefinition object by using the file you created in the previous step:

   $ oc create -f pxe-net-conf.yaml

3. Edit the virtual machine instance configuration file to include the details of the interface and network.

   1. Specify the network and MAC address, if required by the PXE server. If the MAC address is not specified, a value is assigned automatically. However, note that at this time, MAC addresses assigned automatically are not persistent.

      Ensure that bootOrder is set to 1 so that the interface boots first. In this example, the interface is connected to a network called <pxe-net>:

      interfaces:
      - masquerade: {}
        name: default
      - bridge: {}
        name: pxe-net
        macAddress: de:00:00:00:00:de
        bootOrder: 1

      注意

      Boot order is global for interfaces and disks.

   2. Assign a boot device number to the disk to ensure proper booting after operating system provisioning.

      Set the disk bootOrder value to 2:

      devices:
        disks:
        - disk:
            bus: virtio
          name: containerdisk
          bootOrder: 2

   3. Specify that the network is connected to the previously created NetworkAttachmentDefinition. In this scenario, <pxe-net> is connected to the NetworkAttachmentDefinition called <pxe-net-conf>:

      networks:
      - name: default
        pod: {}
      - name: pxe-net
        multus:
          networkName: pxe-net-conf

4. Create the virtual machine instance:

   $ oc create -f vmi-pxe-boot.yaml

1. Wait for the virtual machine instance to run:

   $ oc get vmi vmi-pxe-boot -o yaml | grep -i phase
     phase: Running

2. View the virtual machine instance using VNC:

   $ virtctl vnc vmi-pxe-boot

3. Watch the boot screen to verify that the PXE boot is successful.

4. Log in to the virtual machine instance:

   $ virtctl console vmi-pxe-boot

5. Verify the interfaces and MAC address on the virtual machine and that the interface connected to the bridge has the specified MAC address. In this case, we used eth1 for the PXE boot, without an IP address. The other interface, eth0, got an IP address from OpenShift Container Platform.

   $ ip addr

Procedure

1. To explicitly tell the virtual machine instance that it has more memory available than was requested from the cluster, edit the virtual machine configuration file and set spec.domain.memory.guest to a higher value than spec.domain.resources.requests.memory. This process is called memory overcommitment.

   In this example, 1024M is requested from the cluster, but the virtual machine instance is told that it has 2048M available. As long as there is enough free memory available on the node, the virtual machine instance will consume up to 2048M.

   kind: VirtualMachine
   spec:
     template:
       domain:
       resources:
           requests:
             memory: 1024M
       memory:
           guest: 2048M

   注意

   The same eviction rules as those for pods apply to the virtual machine instance if the node is under memory pressure.

2. Create the virtual machine:

   $ oc create -f <file_name>.yaml

Procedure

1. To disable guest memory overhead accounting, edit the YAML configuration file and set the overcommitGuestOverhead value to true. This parameter is disabled by default.

   kind: VirtualMachine
   spec:
     template:
       domain:
       resources:
           overcommitGuestOverhead: true
           requests:
             memory: 1024M

   注意

   If overcommitGuestOverhead is enabled, it adds the guest overhead to memory limits, if present.

2. Create the virtual machine:

   $ oc create -f <file_name>.yaml

Procedure

1. In your virtual machine configuration, add the resources.requests.memory and memory.hugepages.pageSize parameters to the spec.domain. The following configuration snippet is for a virtual machine that requests a total of 4Gi memory with a page size of 1Gi:

   kind: VirtualMachine
   ...
   spec:
     domain:
       resources:
         requests:
           memory: "4Gi" 1
       memory:
         hugepages:
           pageSize: "1Gi" 2
   ...

   1

   The total amount of memory requested for the virtual machine. This value must be divisible by the page size.

   2

   The size of each huge page. Valid values for x86_64 architecture are 1Gi and 2Mi. The page size must be smaller than the requested memory.

2. Apply the virtual machine configuration:

   $ oc apply -f <virtual_machine>.yaml

Procedure

1. Click Workloads Virtual Machines from the side menu.
2. Select a virtual machine to open the Virtual Machine Overview page.
3. Click the Details tab.
4. Click the pencil icon to the right of the Dedicated Resources field to open the Dedicated Resources window.
5. Select Schedule this workload with dedicated resources (guaranteed policy).
6. Click Save.