--- title: "VM-Operator: Controller — Reconciles the VM CRs" description: >- Information about the VM Operator's controller component its configuration options and the CRD used to define VMs. layout: vm-operator --- # The Controller The controller component (which is part of the manager) monitors custom resources of kind `VirtualMachine`. It creates or modifies other resources in the cluster as required to get the VM defined by the CR up and running. Here is the sample definition of a VM from the ["local-path" example](https://github.com/mnlipp/VM-Operator/tree/main/example/local-path): ```yaml apiVersion: "vmoperator.jdrupes.org/v1" kind: VirtualMachine metadata: namespace: vmop-demo name: test-vm spec: guestShutdownStops: false vm: state: Running maximumCpus: 4 currentCpus: 2 maximumRam: 8Gi currentRam: 4Gi networks: - user: {} disks: - volumeClaimTemplate: metadata: name: system spec: storageClassName: "" selector: matchLabels: app.kubernetes.io/name: vmrunner app.kubernetes.io/instance: test-vm vmrunner.jdrupes.org/disk: system resources: requests: storage: 40Gi - cdrom: image: "" # image: https://download.fedoraproject.org/pub/fedora/linux/releases/38/Workstation/x86_64/iso/Fedora-Workstation-Live-x86_64-38-1.6.iso # image: "Fedora-Workstation-Live-x86_64-38-1.6.iso" display: spice: port: 5910 # Since 3.0.0: # generateSecret: false ``` ## Pod management The central resource created by the controller is a [`Pod`](https://kubernetes.io/docs/concepts/workloads/pods/) with the same name as the VM (`metadata.name`). The pod is created only if `spec.vm.state` is "Running" (default is "Stopped" which deletes the pod)[^oldSts]. Property `spec.guestShutdownStops` (since 2.2.0) controls the effect of a shutdown initiated by the guest. If set to `false` (default) the pod and thus the VM is automatically restarted. If set to `true`, the VM's state is set to "Stopped" when the VM terminates and the pod is deleted. [^oldSts]: Before version 3.4, the operator created a [stateful set](https://kubernetes.io/docs/concepts/workloads/controllers/statefulset/) that in turn created the pod and the PVCs (see below). ## Defining the basics How to define the number of CPUs and the size of the RAM of the VM should be obvious from the example. Note that changes of the current number of CPUs and the current RAM size will be propagated to running VMs. ## Defining disks Maybe the most interesting part is the definition of the VM's disks. This is done by adding one or more `volumeClaimTemplate`s to the list of disks. As its name suggests, such a template is used by the controller to generate a [`PVC`](https://kubernetes.io/docs/concepts/storage/persistent-volumes/). The example template does not define any storage. Rather it references some PV that you must have created first. This may be your first approach if you have existing storage from running the VM outside Kubernetes (e.g. with libvirtd). If you have ceph or some other full fledged storage provider installed and create a new VM, provisioning a disk can happen automatically as shown in this example: ```yaml disks: - volumeClaimTemplate: metadata: name: system spec: storageClassName: rook-ceph-block resources: requests: storage: 40Gi ``` The disk will be available as "/dev/*name*-disk" in the VM, using the string from `.volumeClaimTemplate.metadata.name` as *name*. If no name is defined in the metadata, then "/dev/disk-*n*" is used instead, with *n* being the index of the volume claim template in the list of disks. The name of the generated PVC is the VM's name with "-*name*-disk" (or the generated name) appended: "*vmName*-*name*-disk" (or "*vmName*-disk-*n*"). The definition of the PVC is simply a copy of the information from the `volumeClaimTemplate` (with some additional labels, see below)[^oldStsDisks]. [^oldStsDisks]: Before version 3.4 the `volumeClaimTemplate`s were copied in the definition of the stateful set. As a stateful set appends the started pod's name to the name of the volume claim templates when it creates the PVCs, the PVCs' name were "*name*-disk-*vmName*-0" (or "disk-*n*-*vmName*-0"). PVCs are never removed automatically. Usually, you do not want your VMs disks to be removed when you (maybe accidentally) remove the CR for the VM. To simplify the lookup for an eventual (manual) removal, all PVCs are labeled with "app.kubernetes.io/name: vm-runner", "app.kubernetes.io/instance: *vmName*", and "app.kubernetes.io/managed-by: vm-operator", making it easy to select the PVCs by label in a delete command. ## Choosing an image for the runner The image used for the runner can be configured with [`spec.image`](https://github.com/mnlipp/VM-Operator/blob/7e094e720b7b59a5e50f4a9a4ad29a6000ec76e6/deploy/crds/vms-crd.yaml#L19). This is a mapping with either a single key `source` or a detailed configuration using the keys `repository`, `path` etc. Currently two runner images are maintained. One that is based on Arch Linux (`ghcr.io/mnlipp/org.jdrupes.vmoperator.runner.qemu-arch`) and a second one based on Alpine (`ghcr.io/mnlipp/org.jdrupes.vmoperator.runner.qemu-alpine`). Starting with release 1.0, all versions of runner images and managers that have the same major release number are guaranteed to be compatible. ## Generating cloud-init data *Since: 2.2.0* The optional object `.spec.cloudInit` with sub-objects `.cloudInit.metaData`, `.cloudInit.userData` and `.cloudInit.networkConfig` can be used to provide data for [cloud-init](https://cloudinit.readthedocs.io/en/latest/index.html). The data from the CRD will be made available to the VM by the runner as a vfat formatted disk (see the description of [NoCloud](https://cloudinit.readthedocs.io/en/latest/reference/datasources/nocloud.html)). If `.metaData.instance-id` is not defined, the controller automatically generates it from the CRD's `resourceVersion`. If `.metaData.local-hostname` is not defined, the controller adds this property using the value from `metadata.name`. Note that there are no schema definitions available for `.userData` and `.networkConfig`. Whatever is defined in the CRD is copied to the corresponding cloud-init file without any checks. (The introductory comment `#cloud-config` required at the beginning of `.userData` is generated automatically by the runner.) ## Display secret/password *Since: 2.3.0* You can define a display password using a Kubernetes secret. When you start a VM, the controller checks if there is a secret with labels "app.kubernetes.io/name: vm-runner, app.kubernetes.io/component: display-secret, app.kubernetes.io/instance: *vmname*" in the namespace of the VM definition. The name of the secret can be chosen freely. ```yaml kind: Secret apiVersion: v1 metadata: name: test-vm-display-secret namespace: vmop-demo labels: app.kubernetes.io/name: vm-runner app.kubernetes.io/instance: test-vm app.kubernetes.io/component: display-secret type: Opaque data: display-password: dGVzdC12bQ== # Since 3.0.0: # password-expiry: bmV2ZXI= ``` If such a secret for the VM is found, the VM is configured to use the display password specified. The display password in the secret can be updated while the VM runs[^delay]. Activating/deactivating the display password while a VM runs is not supported by Qemu and therefore requires stopping the VM, adding/removing the secret and restarting the VM. [^delay]: Be aware of the possible delay, see e.g. [here](https://web.archive.org/web/20240223073838/https://ahmet.im/blog/kubernetes-secret-volumes-delay/). *Since: 3.0.0* The secret's `data` can have an additional property `data.password-expiry` which specifies a (base64 encoded) expiry date for the password. Supported values are those defined by qemu (`+n` seconds from now, `n` Unix timestamp, `never` and `now`). Unless `spec.vm.display.spice.generateSecret` is set to `false` in the VM definition (CRD), the controller creates a secret for the display password automatically if none is found. The secret is created with a random password that expires immediately, which makes the display effectively inaccessible until the secret is modified. Note that a password set manually may be overwritten by components of the manager unless the password-expiry is set to "never" or some time in the future. ## Further reading For a detailed description of the available configuration options see the [CRD](https://github.com/mnlipp/VM-Operator/blob/main/deploy/crds/vms-crd.yaml).