Chapter 3. Creating virtual machines

Prerequisites

• Virtualization is enabled on your host system.
• You have a sufficient amount of system resources to allocate to your VMs, such as disk space, RAM, or CPUs. The recommended values might vary significantly depending on the intended tasks and workload of the VMs.

• An operating system (OS) installation source is available locally or on a network. This can be one of the following:

  • An ISO image of an installation medium

  • A disk image of an existing VM installation

    Warning

    Installing from a host CD-ROM or DVD-ROM device is not possible in RHEL 10. If you select a CD-ROM or DVD-ROM as the installation source when using any VM installation method available in RHEL 10, the installation will fail. For more information, see the Red Hat Knowledgebase.

• To create a VM that uses the system connection of libvirt, you must have root privileges or be in the libvirt user group on the host. For more information, see User-space connection types for virtualization.
• Optional: A Kickstart file can be provided for faster and easier configuration of the installation.

• --name: the name of the new machine
• --memory: the amount of allocated memory
• --vcpus: the number of allocated virtual CPUs
• --disk: the type and size of the allocated storage
• --cdrom or --location: the type and location of the OS installation source

• --osinfo: the OS type and version that you intend to install

  Note

  To list all available values for the --osinfo argument, run the virt-install --osinfo list command.

  For more details, you can also run the osinfo-query os command. However, you might need to install the libosinfo-bin package first.

• Create a VM and install an OS from a local ISO file:

  • The following command creates a VM named demo-guest1 that installs the Windows 10 OS from an ISO image locally stored in the /home/username/Downloads/Win10install.iso file. This VM is also allocated with 2048 MiB of RAM and 2 vCPUs, and an 80 GiB qcow2 virtual disk is automatically configured for the VM.

    # virt-install \
        --name demo-guest1 --memory 2048 \
        --vcpus 2 --disk size=80 --osinfo win10 \
        --cdrom /home/username/Downloads/Win10install.iso

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• Create a VM, install an OS from a live CD, and do not create a permanent disk:

  • The following command creates a VM named demo-guest2 that uses the /home/username/Downloads/rhel10.iso image to run a RHEL 10 OS from a live CD. No disk space is assigned to this VM, so changes made during the session will not be preserved. In addition, the VM is allocated with 4096 MiB of RAM and 4 vCPUs.

    # virt-install \
        --name demo-guest2 --memory 4096 --vcpus 4 \
        --disk none --livecd --osinfo rhel10.0 \
        --cdrom /home/username/Downloads/rhel10.iso

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• Create a VM and import an existing disk image:

  • The following command creates a RHEL 10 VM named demo-guest3 that connects to an existing disk image, /home/username/backup/disk.qcow2. This is similar to physically moving a hard drive between machines, so the OS and data available to demo-guest3 are determined by how the image was handled previously. In addition, this VM is allocated with 2048 MiB of RAM and 2 vCPUs.

    # virt-install \
        --name demo-guest3 --memory 2048 --vcpus 2 \
        --osinfo rhel10.0 --import \
        --disk /home/username/backup/disk.qcow2

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    Note that you must use the --osinfo option when importing a disk image. If it is not provided, the performance of the created VM will be negatively affected.

• Create a VM and install an OS from a remote URL:

  • The following command creates a VM named demo-guest4 that installs from the http://example.com/OS-install URL. For the installation to start successfully, the URL must contain a working OS installation tree. In addition, the OS is automatically configured by using the /home/username/ks.cfg kickstart file. This VM is also allocated with 2048 MiB of RAM, 2 vCPUs, and a 160 GiB qcow2 virtual disk.

    # virt-install \
        --name demo-guest4 --memory 2048 --vcpus 2 --disk size=160 \
        --osinfo rhel10.0 --location http://example.com/OS-install \
        --initrd-inject /home/username/ks.cfg --extra-args="inst.ks=file:/ks.cfg console=tty0 console=ttyS0,115200n8"

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    In addition, if you want to host demo-guest4 on an RHEL 10 on an ARM 64 host, include the following lines to ensure that the kickstart file installs the kernel-64k package:

    %packages
    -kernel
    kernel-64k
    %end

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• Create a VM and install an OS in a text-only mode:

  • The following command creates a VM named demo-guest5 that installs from a RHEL10.iso image file in text-only mode, without graphics. It connects the guest console to the serial console. The VM has 16384 MiB of memory, 16 vCPUs, and 280 GiB disk. This kind of installation is useful when connecting to a host over a slow network link.

    # virt-install \
        --name demo-guest5 --memory 16384 --vcpus 16 --disk size=280 \
        --osinfo rhel10.0 --location RHEL10.iso \
        --graphics none --extra-args='console=ttyS0'

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• Create a VM on a remote host:

  • The following command creates a VM named demo-guest6, which has the same configuration as demo-guest5, but resides on the 192.0.2.1 remote host.

    # virt-install \
        --connect qemu+ssh://root@192.0.2.1/system --name demo-guest6 --memory 16384 \
        --vcpus 16 --disk size=280 --osinfo rhel10.0 --location RHEL10.iso \
        --graphics none --extra-args='console=ttyS0'

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• Create a VM on a remote host and use a DASD mediated device as storage:

  • The following command creates a VM named demo-guest-7, which has the same configuration as demo-guest5, but for its storage, it uses a DASD mediated device mdev_30820a6f_b1a5_4503_91ca_0c10ba12345a_0_0_29a8, and assigns it device number 1111.

    # virt-install \
        --name demo-guest7 --memory 16384 --vcpus 16 --disk size=280 \
        --osinfo rhel10.0 --location RHEL10.iso --graphics none \
        --disk none --hostdev mdev_30820a6f_b1a5_4503_91ca_0c10ba12345a_0_0_29a8,address.type=ccw,address.cssid=0xfe,address.ssid=0x0,address.devno=0x1111,boot-order=1 \
        --extra-args 'rd.dasd=0.0.1111'

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    Note that the name of the mediated device available for installation can be retrieved by using the virsh nodedev-list --cap mdev command.

Verification

• If the VM is created successfully, a virt-viewer window opens with a graphical console of the VM and starts the guest OS installation.

Troubleshooting

• If virt-install fails with a cannot find default network error:

  • Ensure that the libvirt-daemon-config-network package is installed:

    # dnf info libvirt-daemon-config-network
    Installed Packages
    Name         : libvirt-daemon-config-network
    [...]

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  • Verify that the libvirt default network is active and configured to start automatically:

    # virsh net-list --all
     Name      State    Autostart   Persistent
    --------------------------------------------
     default   active   yes         yes

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  • If it is not, activate the default network and set it to auto-start:

    # virsh net-autostart default
    Network default marked as autostarted
    
    # virsh net-start default
    Network default started

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    • If activating the default network fails with the following error, the libvirt-daemon-config-network package has not been installed correctly.

      error: failed to get network 'default'
      error: Network not found: no network with matching name 'default'

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      To fix this, re-install libvirt-daemon-config-network:

      # dnf reinstall libvirt-daemon-config-network

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    • If activating the default network fails with an error similar to the following, a conflict has occurred between the default network’s subnet and an existing interface on the host.

      error: Failed to start network default
      error: internal error: Network is already in use by interface ens2

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      To fix this, use the virsh net-edit default command and change the 192.0.2.* values in the configuration to a subnet not already in use on the host.