Alauda Container Platform

Creating Linux Images Based on ISO Using KubeVirt

This document describes a virtual machine solution implemented based on the open-source component KubeVirt. It utilizes KubeVirt virtualization technology to create a Linux operating system image from an ISO image file.

TOC

PrerequisitesConstraints and LimitationsProcedure

Prerequisites

  • All components in the cluster are functioning properly.

  • A Linux image should be prepared in advance. This document uses the Ubuntu operating system as an example.

  • A repository for storing images should be prepared in advance. This document uses the build-harbor.example.cn repository as an example; please replace it according to your actual environment.

Constraints and Limitations

  • When starting KubeVirt, the file system size of the custom image will affect the speed of writing the image to the PVC disk. If the file system is too large, it may result in a prolonged creation time.

  • It is recommended to keep the Linux root partition size below 100G to minimize the initial size. After configuring cloud-init, allocate larger storage for the root partition when creating the virtual machine, and the system will automatically expand it.

Procedure

Convert Linux ISO Image into Docker Image

  1. Navigate to the directory where the ISO image is stored and execute the following command in the terminal to rename the ISO image to ubuntu.iso.

    mv <ISO image name> ubuntu.iso # Replace <ISO image name> with the actual image name, e.g., mv ubuntu-24.04-live-server-amd64.iso ubuntu.iso

  2. Create a Dockerfile by executing the following command.

    touch Dockerfile

  3. Edit the Dockerfile, add the following content, and save it.

    FROM scratch
ADD --chown=107:107 ubuntu.iso /disk/

  4. Build the Docker image by executing the following command.

    docker build -t build-harbor.example.cn/3rdparty/vmdisks/ubuntu-iso:24.04 . # Please replace the repository according to your actual environment

  5. Push the image to the repository by executing the following command.

    docker push build-harbor.example.cn/3rdparty/vmdisks/ubuntu-iso:24.04 # Please replace the repository according to your actual environment

Create Virtual Machine

  1. Enter the Container Platform.

  2. Click Virtualization > Virtual Machines in the left navigation bar.

  3. Click Create Virtual Machine.

  4. Fill in the parameters on the form page as follows. For specific parameters and configurations, please refer to Create Virtual Machine.

    ParameterDescription
    Select ImageChoose the template image for the virtual machine.
    IP AddressKeep default, which will be obtained via DHCP.
    Network ModeUse NAT mode; do not use bridged mode here.

  5. Switch to YAML.

  6. Replace the configuration under the spec.template.spec.domain.devices.disks field with the following content.

          domain:
        devices:
          disks:
            - bootOrder: 1
              cdrom:
                bus: sata
              name: containerdisk
            - disk:
                bus: virtio
              name: cloudinitdisk
            - disk:
                bus: virtio
              name: rootfs
              bootOrder: 10

  7. Add the following content under the spec.template.spec.volumes field.

            - containerDisk:
            image: registry.example.cn:60070/3rdparty/vmdisks/ubuntu-iso:24.04 # Please replace the image according to your actual environment
          name: containerdisk

  8. Review the YAML file; the complete YAML configuration after completion is as follows.

    apiVersion: kubevirt.io/v1alpha3
kind: VirtualMachine
metadata:
  annotations:
    kubevirt.io/latest-observed-api-version: v1
    kubevirt.io/storage-observed-api-version: v1
  labels:
    virtualization.cpaas.io/image-name: debian-2120-x86
    virtualization.cpaas.io/image-os-arch: amd64
    virtualization.cpaas.io/image-os-type: debian
    virtualization.cpaas.io/image-supply-by: public
    vm.cpaas.io/name: aa
  name: aa
spec:
  dataVolumeTemplates:
    - metadata:
        creationTimestamp: null
        labels:
          vm.cpaas.io/reclaim-policy: Delete
          vm.cpaas.io/used-by: aa
        name: aa-rootfs
      spec:
        pvc:
          accessModes:
            - ReadWriteOnce
          resources:
            requests:
              storage: 100Gi
          storageClassName: vm-cephrbd
          volumeMode: Block
        source:
          http:
            url: http://192.168.254.12/kube-debian-12.2.0-x86-out.qcow2
  running: true
  template:
    metadata:
      annotations:
        cpaas.io/creator: test@example.io
        cpaas.io/display-name: ""
        cpaas.io/updated-at: 2024-09-09T03:49:08Z
        kubevirt.io/latest-observed-api-version: v1
        kubevirt.io/storage-observed-api-version: v1
      creationTimestamp: null
      labels:
        virtualization.cpaas.io/image-name: debian-2120-x86
        virtualization.cpaas.io/image-os-arch: amd64
        virtualization.cpaas.io/image-os-type: debian
        virtualization.cpaas.io/image-supply-by: public
        vm.cpaas.io/name: aa
    spec:
      accessCredentials:
        - sshPublicKey:
            propagationMethod:
              qemuGuestAgent:
                users:
                  - root
            source:
              secret:
                secretName: test-xeon
      affinity:
        nodeAffinity: {}
      architecture: amd64
      domain:
        devices:
          disks:
            - bootOrder: 1
              cdrom:
                bus: sata
              name: containerdisk
            - disk:
                bus: virtio
              name: cloudinitdisk
            - disk:
                bus: virtio
              name: rootfs
              bootOrder: 10
           interfaces:
            - bridge: {}
              name: default
        machine:
          type: q35
        resources:
          limits:
            cpu: "1"
            memory: 2Gi
          requests:
            cpu: "1"
            memory: 2Gi
      networks:
        - name: default
          pod: {}
      nodeSelector:
        kubernetes.io/arch: amd64
        vm.cpaas.io/baremetal: "true"
      volumes:
        - containerDisk:
            image: registry.example.cn:60070/3rdparty/vmdisks/ubuntu-iso:24.04 # Please replace the image according to your actual environment
          name: containerdisk
        - cloudInitConfigDrive:
            userData: |-
              #cloud-config
              disable_root: false
              ssh_pwauth: false
              users:
                - default
                - name: root
                  lock_passwd: false
                  hashed_passwd: ""
          name: cloudinitdisk
        - dataVolume:
            name: aa-rootfs
          name: rootfs

  9. Click Create.

  10. Click Actions > VNC Login.

  11. When prompted with press any key boot from CD or DVD, press any key to enter the Windows installation program; if you do not see the prompt, click Send Remote Command in the upper left corner of the page, and then click Ctrl-Alt-Delete from the dropdown menu to reboot the server.

    Note: If a message appears at the top of the virtual machine detail page stating Current virtual machine has configuration changes that require a restart to take effect. Please restart., you can ignore this message; a restart is not necessary.

Install Linux Operating System

  1. After entering the installation page, follow the installation guide to proceed. This document gives an example of installing the Ubuntu operating system; the configuration items during the installation process of different operating systems are generally similar, and thus will not be elaborated further. Some configuration items are explained below.

    ConfigurationDescription
    Installation TypeIt is recommended to use a minimal installation to minimize the image size.
    Storage ConfigurationChoose custom storage. Format the disk to ext4 or xfs format and mount it to the root partition (/).
    Note: Do not use LVM for disk partitioning (Create volume group (LVM)).
    SSH ConfigurationChoose to install the OpenSSH tools for SSH access.

  2. Wait for the installation to complete.

Modify YAML File

  1. Enter the Container Platform.

  2. In the left navigation bar, click Virtualization > Virtual Machines.

  3. Click on the Virtual Machine Name in the list to enter the details page.

  4. Click Stop.

  5. Click Actions > Update in the upper right corner.

  6. Switch to YAML.

  7. Confirm that the disk named rootfs under spec.template.spec.domain.devices.disks has a bootOrder of 1. If it is not 1, modify it to 1.

  8. Delete the relevant content for the disk named containerdisk under spec.template.spec.domain.devices.disks; the specific content to delete is as follows.

                - bootOrder: 1
              cdrom:
                bus: sata
              name: containerdisk

  9. Delete the relevant content for the disk named containerdisk under spec.template.spec.volumes; the specific content to delete is as follows.

            - containerDisk:
            image: registry.example.cn:60070/3rdparty/vmdisks/ubuntu-iso:24.04
          name: containerdisk

  10. Click Update.

  11. Click Start.

Install Required Software and Modify Configuration

Note: The following commands and configuration files may vary slightly between different operating systems; please adjust according to your actual environment.

  1. Enter your username and password to log in to the operating system.

  2. Switch to root user privileges.

  3. Install the software packages.

    • For CentOS series, execute the command:

      yum install cloud-utils cloud-init qemu-guest-agent vim

    • For Debian series, execute the command:

      apt install cloud-init cloud-guest-utils qemu-guest-agent vim

  4. Edit the SSHD configuration file.

    1. Execute the following command to edit the sshd_config file.

      vim /etc/ssh/sshd_config

    2. Add the following configurations.

      PermitRootLogin yes  # Allow the root user to log in with a password
PubkeyAuthentication yes  # Allow key-based login

    3. Save the modified configuration.

  5. Execute the following command to delete the default password for the root user.

    passwd -d root

  6. Modify the source address file.

    1. Execute the following command to modify the system's source address file and change the address to a suitable mirror site address.

      vim /etc/apt/sources.list.d/ubuntu.sources

    2. Save the configuration after modifications.

  7. Modify the cloud-init configuration to automatically expand the root directory.

    1. Execute the following command to edit the cloud.cfg configuration file.

      vim /etc/cloud/cloud.cfg

    2. Add the following configuration content.

      runcmd:
  - [growpart, /dev/vda, 1]  # The growpart command is used to extend the partition on the disk, which will extend the /dev/vda1 partition.
  - [xfs_growfs, /dev/vda1]  # The xfs_growfs command is used to extend the XFS file system to occupy all available space on the partition. /dev/vda1 is the partition where the file system to be extended is located. After extending the partition, using xfs_growfs ensures that the file system itself is also expanded to the new partition size.

    3. Save the configuration after modifications.

  8. After completing the configuration, shut down the operating system.

Export and Use the Custom Linux Image

For specific operations, please refer to Export Virtual Machine Image.