Enable or disable VM Runtime on GDC

This document shows you how to enable or disable VM Runtime on Google Distributed Cloud by either updating the VMRuntime custom resource or running bmctl commands.

Before you begin

To enable or disable VM Runtime on GDC, you need access to the following resources and tools:

Access to GKE on Bare Metal version 1.12.0 (anthosBareMetalVersion: 1.12.0) or higher cluster. You can use any cluster type capable of running workloads. If needed, try GKE on Bare Metal on Compute Engine or see the cluster creation overview.
The bmctl command-line tool. For more information, see Download and install the bmctl tool.

Enable VM Runtime on GDC

VM Runtime on GDC is automatically installed in GKE on Bare Metal version 1.10 or higher, but is disabled by default. Before you can run VM resources in your GKE on Bare Metal, you must enable the VM Runtime on GDC.

bmctl

To enable the runtime, use the bmctl tool:
```
bmctl enable vmruntime --kubeconfig KUBECONFIG_PATH
```
Provide the path to the kubeconfig file for your cluster. GKE on Bare Metal generates the kubeconfig file on the admin workstation when you create a cluster. By default, the path is bmctl-workspace/CLUSTER_NAME/CLUSTER_NAME-kubeconfig.

If VM Runtime on GDC is already enabled, the command returns an error.

Additional settings, such as for emulation or image format, can be configured by editing the VMRuntime custom resource.

Custom resource

To enable the runtime, update the VMRuntime custom resource. This custom resource is installed by default.

Edit the VMRuntime custom resource:
```
kubectl edit vmruntime
```
Set enabled:true in the spec:
```
apiVersion: vm.cluster.gke.io/v1
kind: VMRuntime
metadata:
  name: vmruntime
spec:
  enabled: true
  # useEmulation defaults to "false" if not set.
  useEmulation: true
  # vmImageFormat defaults to "qcow2" if not set.
  vmImageFormat: qcow2
```
In the preceding spec section, the following values can be set:
- enabled: set to true to enable VM Runtime on GDC
- useEmulation: If your node doesn't support hardware virtualization, or you aren't sure, set the value to true. If available, hardware virtualization provides better performance than software emulation. The useEmulation field defaults to false, if it isn't specified.
- vmImageFormat: Supports two disk image format values: raw and qcow2. If you don't set vmImageFormat, the VM Runtime on GDC uses the raw disk image format to create VMs. The raw format may provide improved performance over qcow2, a copy on write format, but may use more disk. For more information about the image formats for your VM, see Disk image file formats in the QEMU documentation.
Save the custom resource in your editor.
Verify that the VMRuntime custom resource is enabled:
```
kubectl describe vmruntime vmruntime
```
The details of the VMRuntime custom resource include a Status section. VM Runtime on GDC is enabled and working when VMRuntime.Status.Ready shows as true.

Disable VM Runtime on GDC

When you no longer need to use VM Runtime on GDC, you can disable this feature.

bmctl

To disable the runtime, use the bmctl tool:
```
bmctl disable vmruntime --kubeconfig KUBECONFIG_PATH \
  --force=true
```
Provide the path to the kubeconfig file for your cluster and values for the following configuration options:
- --force: Set to true to confirm you want to delete existing VM resources. The default value is false.

Custom resource

To disable the runtime, update the VMRuntime custom resource:

Edit the VMRuntime custom resource:
```
kubectl edit vmruntime
```

Set enabled:false in the spec:

apiVersion: vm.cluster.gke.io/v1`
kind: VMRuntime
metadata:
  name: vmruntime
spec:
  enabled: false
  useEmulation: true
  vmImageFormat: qcow2

Save the updated custom resource specification in your editor.
To verify that the VMRuntime custom resource is disabled, view the pods that run in the vm-system namespace:
```
kubectl get pods --namespace vm-system
```
VM Runtime on GDC is disabled when only the pods that belong to the vmruntime-controller-manager deployment are running in the namespace.

Understand the behavior for running VMs

The baremetal.cluster.gke.io/vmrumtime-force-disableannotation can be used on VM Runtime on GDC resource to define the behavior when the runtime is disabled while VMs are running in the cluster.

The following example shows that the value of this annotation is set to false by default:

// VM runtime yaml file
apiVersion: vm.cluster.gke.io/v1
kind: VMRuntime
metadata:
  annotations:
    baremetal.cluster.gke.io/vmrumtime-force-disable: "false"
  name: vmruntime
[...]

When this annotation is set to false, VM Runtime on GDC tries to protect running VMs. Delete all running VMs before the VM Runtime on GDC is disabled, or specify the --force=true parameter with the bmctl disable vmruntime command as shown in the previous section.

The following table explains what happens to running VMs when this annotation is set to true or false and if you specify the --force=true parameter or not:

Cluster state	--force parameter	vmrumtime-force-disable annotation	Behavior
No VMs	N/A	N/A	Disable VM Runtime on GDC.
Existing VMs	True	True	Delete all running VMs and the related resources. Disable the VM Runtime on GDC.
	True	False	Delete all running VMs and the related resources. Disable the VM Runtime on GDC.
	False	True	Prompt to delete running VMs and related resources. When all running VMs have been deleted, disable VM Runtime on GDC.
	False	False	Don't delete any existing VMs that are running. Don't disable the VM Runtime on GDC. The `bmctl` command returns an error.

VM Runtime on GDC preflight check

The VM Runtime on GDC preflight check validates a set of prerequisites on the machine's environment before using VM Runtime on GDC and VMs. VM creation is blocked if VM Runtime on GDC preflight check failed. The VM Runtime on GDC preflight check runs automatically when spec.enabled is set to true.

kubectl label nodes NODE_NAME "kubevm.io/VM-SkipSchedule"= --kubeconfig KUBECONFIG_PATH

The VM Runtime on GDC preflight check runs when you perform any of the following operations:

Enable VM Runtime on GDC
Enable VM Runtime on GDC features, such as useEmulation
Upgrade clusters
Remove kubevm.io/VM-SkipSchedule label at nodes
Independently create VM Runtime on GDC preflight check object by running the bmctl check vmruntimepfc --kubeconfig KUBECONFIG_PATH command or applying a VMRuntimePreflightCheck YAML manifest.

You can launch VMs when the latest VM Runtime on GDC preflight check succeeds. If the preflight check fails, VM creation is blocked and you get preflight check errors.

Verifying preflight check success

To verify if the preflight checks were successful, run the following commands:

Find the last preflight checks performed:

kubectl get vmruntimepfc -n vm-system --kubeconfig KUBECONFIG_PATH

The output should look like the following sample:

NAME                                                             PASS    AGE
vmruntime-preflight-check-6ee61513-ea5d-4340-9374-90396cac129e   false   42s
vmruntime-preflight-check-f8d71751-a01c-471e-bab5-3370fc2addd5   true    21s

To find the status of a preflight check, run the following command:

kubectl get vmruntime vmruntime -o yaml --kubeconfig KUBECONFIG_PATH

...
  preflightCheckSummary:
  preflightCheckSummary:
    featureStatuses:
      CPU:
        passed: true
      KVM:
        passed: true
    preflightCheckName: vmruntime-preflight-check-f8d71751-a01c-471e-bab5-3370fc2addd5
    preflightCheckPassed: true
...

Debug preflight check fails

If the preflight check fails, perform the following steps to debug:

Find the last preflight checks performed.
```
kubectl get vmruntimepfc -n vm-system
```

Check the status of that preflight check for details.

kubectl get vmruntimepfc -n vm-system \
    vmruntime-preflight-check-6ee61513-ea5d-4340-9374-90396cac129e -o yaml \
    --kubeconfig KUBECONFIG_PATH

...
status:
checks:
  worker-0--52229ee15841099-22c41577139a7b8c.lab.anthos:
    passed: false
    results:
    - checkName: CPU
      passed: true
    - checkName: KVM
      message: |
        command terminated with exit code 1
        ls: /mnt/dev/kvm: No such file or directory
      passed: false
...

Fix the issue and run VM Runtime on GDC preflight check again. The following shows an example VMRuntimePreflightCheck YAML manifest:

apiVersion: vm.cluster.gke.io/v1
kind: VMRuntimePreflightCheck
metadata:
  name: vmruntime-preflight-check-manual
  namespace: vm-system

What's next

Create a VM in GKE on Bare Metal.