#Creating Linux Images Based on ISO Using KubeVirt

#Upload the Linux ISO to a DataVolume

Upload the ISO file directly to the cluster storage using the CDI upload mechanism, without building a container image.

1. Create an upload-type DataVolume by saving the following YAML to a file named dv-iso-upload.yaml. Adjust the storage size based on the actual ISO file size.

   apiVersion: cdi.kubevirt.io/v1beta1
   kind: DataVolume
   metadata:
     name: iso-upload-dv
     namespace: default
     annotations:
       cdi.kubevirt.io/storage.bind.immediate.requested: "true"
   spec:
     source:
       upload: {}
     storage:
       accessModes:
         - ReadWriteOnce
       resources:
         requests:
           storage: 8Gi
       storageClassName: vm-cephrbd  # Replace with your actual StorageClass
       volumeMode: Block

2. Execute the following command to create the DataVolume.

   kubectl apply -f dv-iso-upload.yaml

3. Wait for the DataVolume to enter the UploadReady phase.

   kubectl get dv iso-upload-dv -w
   # The PHASE column should show UploadReady

4. Set up port-forwarding to the CDI upload proxy.

   kubectl port-forward -n cdi svc/cdi-uploadproxy 8443:443 &

5. Obtain an authentication token.

   TOKEN=$(kubectl create token default -n default)

6. Upload the ISO file using curl. Replace the file path with the actual path to your ISO.

   curl -v --insecure \
     -H "Authorization: Bearer ${TOKEN}" \
     --data-binary @/path/to/ubuntu-24.04-live-server-amd64.iso \
     "https://localhost:8443/v1beta1/upload"

   Note: The --insecure flag is used to skip self-signed certificate verification. In a production environment, configure proper certificates. Large file uploads may take a long time; ensure network stability.

7. Verify that the DataVolume status changes to Succeeded.

   kubectl get dv iso-upload-dv
   # The PHASE column should show Succeeded

#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.

   Parameter	Description
   Select Image	Choose the template image for the virtual machine.
   IP Address	Keep default, which will be obtained via DHCP.
   Network Mode	Use 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. The ISO DataVolume is mounted as a CDROM with the highest boot priority, and the rootfs disk is used as the installation target.

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

7. Replace the spec.template.spec.volumes field with the following content. The ISO is referenced as a DataVolume instead of a container image.

         volumes:
           - dataVolume:
               name: iso-upload-dv
             name: iso-disk
           - cloudInitConfigDrive:
               userData: |-
                 #cloud-config
                 disable_root: false
                 ssh_pwauth: false
                 users:
                   - default
                   - name: root
                     lock_passwd: false
                     hashed_passwd: "<hash>"  # Generate with: mkpasswd --method=SHA-512 --rounds=4096
             name: cloudinitdisk
           - dataVolume:
               name: aa-rootfs
             name: rootfs

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:
             blank: {}
     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: iso-disk
               - 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:
           - dataVolume:
               name: iso-upload-dv
             name: iso-disk
           - cloudInitConfigDrive:
               userData: |-
                 #cloud-config
                 disable_root: false
                 ssh_pwauth: false
                 users:
                   - default
                   - name: root
                     lock_passwd: false
                     hashed_passwd: "<hash>"  # Generate with: mkpasswd --method=SHA-512 --rounds=4096
             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 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.

   Configuration	Description
   Installation Type	It is recommended to use a minimal installation to minimize the image size.
   Storage Configuration	Choose 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 Configuration	Choose 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 ISO disk named iso-disk under spec.template.spec.domain.devices.disks; the specific content to delete is as follows.

               - bootOrder: 1
                 cdrom:
                   bus: sata
                 name: iso-disk

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

           - dataVolume:
               name: iso-upload-dv
             name: iso-disk

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.