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Chapter 2. Preparing RHEL to host virtual machines

To use virtualization in RHEL 10, you must install virtualization packages and ensure your system is configured to host virtual machines (VMs).

To set up a KVM hypervisor and create virtual machines (VMs) on an AMD64 or Intel 64 system running RHEL 10, start the necessary services.

Prerequisites

  • Red Hat Enterprise Linux 10 is installed and registered on your host machine.

  • Your system meets the following hardware requirements to work as a virtualization host:

    • The architecture of your host machine supports KVM virtualization.

    • The following minimum system resources are available:

      • 6 GB free disk space for the host, plus another 6 GB for each intended VM.
      • 2 GB of RAM for the host, plus another 2 GB for each intended VM.

Procedure

  1. Install the virtualization hypervisor packages. 

    # dnf install qemu-kvm libvirt virt-install virt-viewer
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  2. Start the virtualization services: 

    # for drv in qemu network nodedev nwfilter secret storage interface; do systemctl start virt${drv}d{,-ro,-admin}.socket; done
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Verification

  1. Verify that your system is prepared to be a virtualization host: 

    # virt-host-validate
[...]
QEMU: Checking for device assignment IOMMU support         : PASS
QEMU: Checking if IOMMU is enabled by kernel               : WARN (IOMMU appears to be disabled in kernel. Add intel_iommu=on to kernel cmdline arguments)
LXC: Checking for Linux >= 2.6.26                          : PASS
[...]
LXC: Checking for cgroup 'blkio' controller mount-point    : PASS
LXC: Checking if device /sys/fs/fuse/connections exists    : FAIL (Load the 'fuse' module to enable /proc/ overrides)
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  2. If all virt-host-validate checks return a PASS value, your system is prepared for creating VMs.

    If any of the checks return a FAIL value, follow the displayed instructions to fix the problem.

    If any of the checks return a WARN value, consider following the displayed instructions to improve virtualization capabilities.

Troubleshooting

  • If KVM virtualization is not supported by your host CPU, virt-host-validate generates the following output: 

    QEMU: Checking for hardware virtualization: FAIL (Only emulated CPUs are available, performance will be significantly limited)
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    However, VMs on such a host system will fail to boot, rather than have performance problems.

    To work around this, you can change the <domain type> value in the XML configuration of the VM to qemu. Note, however, that Red Hat does not support VMs that use the qemu domain type, and setting this is highly discouraged in production environments.

To use certain features on a virtual machine (VM) hosted on your RHEL 10 system, you must first configure the VM to use the QEMU Guest Agent (GA).

For a complete list of these features, see Virtualization features that require QEMU Guest Agent.

2.2.1. Enabling QEMU Guest Agent on Windows guests
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To allow a RHEL host to perform a certain subset of operations on a Windows virtual machine (VM), you must enable the QEMU Guest Agent (GA). To do so, add a storage device that contains the QEMU Guest Agent installer to an existing VM or when creating a new VM, and install the drivers on the Windows guest operating system.

To install the Guest Agent (GA) by using the graphical interface, see the procedure below. To install the GA on a command line, use the Microsoft Windows Installer (MSI).

Prerequisites

Procedure

  1. In the Windows guest operating system, open the File Explorer application.
  2. Click This PC.
  3. In the Devices and drives pane, open the virtio-win medium.
  4. Open the guest-agent folder.

  5. Based on the operating system installed on the VM, run one of the following installers:

    • If using a 32-bit operating system, run the qemu-ga-i386.msi installer.
    • If using a 64-bit operating system, run the qemu-ga-x86_64.msi installer.

  6. Optional: If you want to use the para-virtualized serial driver (virtio-serial) as the communication interface between the host and the Windows guest, verify that the virtio-serial driver is installed on the Windows guest.

    For more information about installing virtio drivers, see: Installing virtio drivers on a Windows guest.

Verification

  1. On your Windows VM, navigate to the Services window.

    Computer Management > Services

  2. Ensure that the status of the QEMU Guest Agent service is Running.

2.2.2. Virtualization features that require QEMU Guest Agent
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If you enable QEMU Guest Agent (GA) on a virtual machine (VM), you can use the following commands on your host to manage the VM:

virsh shutdown --mode=agent
This shutdown method is more reliable than virsh shutdown --mode=acpi, because virsh shutdown used with QEMU GA is guaranteed to shut down a cooperative guest in a clean state.
virsh domfsfreeze and virsh domfsthaw
Freezes the guest file system in isolation.
virsh domfstrim

Instructs the guest to trim its file system, which helps to reduce the data that needs to be transferred during migrations.

Important

If you want to use this command to manage a Linux VM, you must also set the following SELinux boolean in the guest operating system: 

# setsebool virt_qemu_ga_read_nonsecurity_files on
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virsh domtime
Queries or sets the guest’s clock.
virsh setvcpus --guest
Instructs the guest to take CPUs offline, which is useful when CPUs cannot be hot-unplugged.
virsh domifaddr --source agent
Queries the guest operating system’s IP address by using QEMU GA. For example, this is useful when the guest interface is directly attached to a host interface.
virsh domfsinfo
Shows a list of mounted file systems in the running guest.
virsh set-user-password
Sets the password for a given user account in the guest.
virsh set-user-sshkeys

Edits the authorized SSH keys file for a given user in the guest.

Important

If you want to use this command to manage a Linux VM, you must also set the following SELinux boolean in the guest operating system: 

# setsebool virt_qemu_ga_manage_ssh on
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2.3. Setting up the web console to manage virtual machines
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Before using the RHEL 10 web console to manage virtual machines (VMs), you must install the web console virtual machine plug-in on the host.

Prerequisites

Procedure

  • Install the cockpit-machines plug-in. 

    # dnf install cockpit-machines
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Verification

  1. Log in to the RHEL 10 web console.

  2. If the installation was successful, Virtual Machines appears in the web console side menu.

    Image displaying the virtual machine tab of the web console.
    View larger image
    Image displaying the virtual machine tab of the web console.
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