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Health Check

When configuring liveness and readiness probes for a virtual machine, the process is similar to that of Kubernetes. This article explains how to configure health check parameters for a virtual machine through YAML.

However, note that you must modify the YAML configuration after the virtual machine is created successfully and is powered off.

Configure an HTTP Liveness Probe

  1. Configure livenessProbe.httpGet in spec.template.spec.

  2. Modify cloudInitNoCloud to start an HTTP server.

    Click to view the YAML example 
            apiVersion: kubevirt.io/v1
        kind: VirtualMachine
        metadata:
          annotations:
            kubevirt.io/latest-observed-api-version: v1
            kubevirt.io/storage-observed-api-version: v1
            virtnest.io/alias-name: ''
            virtnest.io/image-secret: ''
            virtnest.io/image-source: docker
            virtnest.io/os-image: release-ci.daocloud.io/virtnest/system-images/ubuntu-22.04-x86_64:v1
          creationTimestamp: '2024-10-15T02:39:45Z'
          finalizers:
            - kubevirt.io/virtualMachineControllerFinalize
          generation: 1
          labels:
            virtnest.io/os-family: Ubuntu
            virtnest.io/os-version: '22.04'
          name: test-probe
          namespace: amamba-team
          resourceVersion: '254032135'
          uid: 6d92779d-7415-4721-8c7b-a2dde163d758
        spec:
          dataVolumeTemplates:
            - metadata:
                creationTimestamp: null
                name: test-probe-rootdisk
                namespace: amamba-team
              spec:
                pvc:
                  accessModes:
                    - ReadWriteOnce
                  resources:
                    requests:
                      storage: 10Gi
                  storageClassName: hwameistor-storage-lvm-hdd
                source:
                  registry:
                    url: >-
                  docker://release-ci.daocloud.io/virtnest/system-images/ubuntu-22.04-x86_64:v1
          runStrategy: Halted
          template:
            metadata:
              creationTimestamp: null
            spec:
              architecture: amd64
              domain:
                cpu:
                  cores: 1
                  sockets: 1
                  threads: 1
                devices:
                  disks:
                    - bootOrder: 1
                      disk:
                        bus: virtio
                      name: rootdisk
                    - disk:
                        bus: virtio
                      name: cloudinitdisk
                  interfaces:
                    - masquerade: {}
                      name: default
                machine:
                  type: q35
                memory:
                  guest: 2Gi
                resources:
                  requests:
                    memory: 2Gi
              networks:
                - name: default
                  pod: {}
              livenessProbe:
                initialDelaySeconds: 120
                periodSeconds: 20
                httpGet:
                  port: 1500
                timeoutSeconds: 10
              volumes:
                - dataVolume:
                    name: test-probe-rootdisk
                  name: rootdisk
                - cloudInitNoCloud:
                    userData: |
                      #cloud-config
                      ssh_pwauth: true
                      disable_root: false
                      chpasswd: {"list": "root:dangerous", expire: False}
                      runcmd:
                        - sed -i "/#\?PermitRootLogin/s/^.*$/PermitRootLogin yes/g" /etc/ssh/sshd_config
                        - systemctl restart ssh.service
                        - dhclient -r && dhclient
                        - apt-get update && apt-get install -y ncat
                        - ["systemd-run", "--unit=httpserver", "ncat", "-klp", "1500", "-e", '/usr/bin/echo -e HTTP/1.1 200 OK\nContent-Length: 12\n\nHello World!']
                  name: cloudinitdisk

  3. The userData configuration may differ depending on the operating system (such as Ubuntu/Debian or CentOS). The main differences are:

    • Package manager:

      Ubuntu/Debian uses apt-get as the package manager. CentOS uses yum as the package manager.

    • SSH service restart command:

      Ubuntu/Debian uses systemctl restart ssh.service. CentOS uses systemctl restart sshd.service (note that CentOS 7 and earlier versions use service sshd restart).

    • Package to install:

      Ubuntu/Debian installs ncat. CentOS installs nmap-ncat (because ncat may not be available in the default CentOS repositories).

Configure a TCP Liveness Probe

Configure livenessProbe.tcpSocket in spec.template.spec.

Click to view the YAML example 
    apiVersion: kubevirt.io/v1
    kind: VirtualMachine
    metadata:
      annotations:
        kubevirt.io/latest-observed-api-version: v1
        kubevirt.io/storage-observed-api-version: v1
        virtnest.io/alias-name: ''
        virtnest.io/image-secret: ''
        virtnest.io/image-source: docker
        virtnest.io/os-image: release-ci.daocloud.io/virtnest/system-images/ubuntu-22.04-x86_64:v1
      creationTimestamp: '2024-10-15T02:39:45Z'
      finalizers:
        - kubevirt.io/virtualMachineControllerFinalize
      generation: 1
      labels:
        virtnest.io/os-family: Ubuntu
        virtnest.io/os-version: '22.04'
      name: test-probe
      namespace: amamba-team
      resourceVersion: '254032135'
      uid: 6d92779d-7415-4721-8c7b-a2dde163d758
    spec:
      dataVolumeTemplates:
        - metadata:
            creationTimestamp: null
            name: test-probe-rootdisk
            namespace: amamba-team
          spec:
            pvc:
              accessModes:
                - ReadWriteOnce
              resources:
                requests:
                  storage: 10Gi
              storageClassName: hwameistor-storage-lvm-hdd
            source:
              registry:
                url: >-
              docker://release-ci.daocloud.io/virtnest/system-images/ubuntu-22.04-x86_64:v1
      runStrategy: Halted
      template:
        metadata:
          creationTimestamp: null
        spec:
          architecture: amd64
          domain:
            cpu:
              cores: 1
              sockets: 1
              threads: 1
            devices:
              disks:
                - bootOrder: 1
                  disk:
                    bus: virtio
                  name: rootdisk
                - disk:
                    bus: virtio
                  name: cloudinitdisk
              interfaces:
                - masquerade: {}
                  name: default
            machine:
              type: q35
            memory:
              guest: 2Gi
            resources:
              requests:
                memory: 2Gi
          networks:
            - name: default
              pod: {}
          livenessProbe:
            initialDelaySeconds: 120
            periodSeconds: 20
            tcpSocket:
              port: 1500
            timeoutSeconds: 10
          volumes:
            - dataVolume:
                name: test-probe-rootdisk
              name: rootdisk
            - cloudInitNoCloud:
                userData: |
                  #cloud-config
                  ssh_pwauth: true
                  disable_root: false
                  chpasswd: {"list": "root:dangerous", expire: False}
                  runcmd:
                    - sed -i "/#\?PermitRootLogin/s/^.*$/PermitRootLogin yes/g" /etc/ssh/sshd_config
                    - systemctl restart ssh.service
                    - dhclient -r && dhclient
                    - apt-get update && apt-get install -y ncat
                    - ["systemd-run", "--unit=httpserver", "ncat", "-klp", "1500", "-e", '/usr/bin/echo -e HTTP/1.1 200 OK\nContent-Length: 12\n\nHello World!']
              name: cloudinitdisk

Configure Readiness Probes

Configure readiness in spec.template.spec.

Click to view the YAML example 
    apiVersion: kubevirt.io/v1
    kind: VirtualMachine
    metadata:
      annotations:
        kubevirt.io/latest-observed-api-version: v1
        kubevirt.io/storage-observed-api-version: v1
        virtnest.io/alias-name: ''
        virtnest.io/image-secret: ''
        virtnest.io/image-source: docker
        virtnest.io/os-image: release-ci.daocloud.io/virtnest/system-images/ubuntu-22.04-x86_64:v1
      creationTimestamp: '2024-10-15T02:39:45Z'
      finalizers:
        - kubevirt.io/virtualMachineControllerFinalize
      generation: 1
      labels:
        virtnest.io/os-family: Ubuntu
        virtnest.io/os-version: '22.04'
      name: test-probe
      namespace: amamba-team
      resourceVersion: '254032135'
      uid: 6d92779d-7415-4721-8c7b-a2dde163d758
    spec:
      dataVolumeTemplates:
        - metadata:
            creationTimestamp: null
            name: test-probe-rootdisk
            namespace: amamba-team
          spec:
            pvc:
              accessModes:
                - ReadWriteOnce
              resources:
                requests:
                  storage: 10Gi
              storageClassName: hwameistor-storage-lvm-hdd
            source:
              registry:
                url: >-
              docker://release-ci.daocloud.io/virtnest/system-images/ubuntu-22.04-x86_64:v1
      runStrategy: Halted
      template:
        metadata:
          creationTimestamp: null
        spec:
          architecture: amd64
          domain:
            cpu:
              cores: 1
              sockets: 1
              threads: 1
            devices:
              disks:
                - bootOrder: 1
                  disk:
                    bus: virtio
                  name: rootdisk
                - disk:
                    bus: virtio
                  name: cloudinitdisk
              interfaces:
                - masquerade: {}
                  name: default
            machine:
              type: q35
            memory:
              guest: 2Gi
            resources:
              requests:
                memory: 2Gi
          networks:
            - name: default
              pod: {}
          readiness:
            initialDelaySeconds: 120
            periodSeconds: 20
            httpGet:
              port: 1500
            timeoutSeconds: 10
          volumes:
            - dataVolume:
                name: test-probe-rootdisk
              name: rootdisk
            - cloudInitNoCloud:
                userData: |
                  #cloud-config
                  ssh_pwauth: true
                  disable_root: false
                  chpasswd: {"list": "root:dangerous", expire: False}
                  runcmd:
                    - sed -i "/#\?PermitRootLogin/s/^.*$/PermitRootLogin yes/g" /etc/ssh/sshd_config
                    - systemctl restart ssh.service
                    - dhclient -r && dhclient
                    - apt-get update && apt-get install -y ncat
                    - ["systemd-run", "--unit=httpserver", "ncat", "-klp", "1500", "-e", '/usr/bin/echo -e HTTP/1.1 200 OK\nContent-Length: 12\n\nHello World!']
              name: cloudinitdisk

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