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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). The specific steps to do this vary based on your CPU architecture.

Before creating virtual machines (VMs) on an AMD64 or Intel 64 system running RHEL 10, you must first set up a KVM hypervisor on the system.

Prerequisites

  • Red Hat Enterprise Linux 10 is installed and registered on your host machine. For instructions, see the RHEL installation guide.

  • 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

  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

Verification

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

    # virt-host-validate

    Example output: 

    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)

  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)

    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.

Before creating virtual machines (VMs) on an IBM Z system running RHEL 10, you must first set up a KVM hypervisor on the system.

Prerequisites

  • Red Hat Enterprise Linux 10 is installed and registered on your host machine. For instructions, see the RHEL installation guide.

  • 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.
    • 4 CPUs on the host. VMs can generally run with a single assigned vCPU, but Red Hat recommends assigning 2 or more vCPUs per VM to avoid VMs becoming unresponsive during high load.
  • Your IBM Z host system is using an IBM z14 CPU or later.

  • RHEL 10 is installed on a logical partition (LPAR). In addition, the LPAR supports the start-interpretive execution (SIE) virtualization functions.

    To verify this, search for sie in your /proc/cpuinfo file. 

    # grep sie /proc/cpuinfo
features        : esan3 zarch stfle msa ldisp eimm dfp edat etf3eh highgprs te sie

Procedure

  1. Install the virtualization packages: 

    # dnf install qemu-kvm libvirt virt-install

  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

Verification

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

    # virt-host-validate
[...]
QEMU: Checking if device /dev/kvm is accessible             : PASS
QEMU: Checking if device /dev/vhost-net exists              : PASS
QEMU: Checking if device /dev/net/tun exists                : PASS
QEMU: Checking for cgroup 'memory' controller support       : PASS
QEMU: Checking for cgroup 'memory' controller mount-point   : PASS
[...]

  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)

    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.

Before creating virtual machines (VMs) on a 64-bit system (also known as ARM 64 or AArch64) running RHEL 10, you must first set up a KVM hypervisor on the system.

Prerequisites

  • Red Hat Enterprise Linux 10 is installed and registered on your host machine. For instructions, see the RHEL installation guide.

  • The following minimum system resources are available:

    • 6 GB free disk space for the host, plus another 6 GB for each intended guest.
    • 4 GB of RAM for the host, plus another 4 GB for each intended guest.

Procedure

  1. Install the virtualization packages: 

    # dnf install qemu-kvm libvirt virt-install

  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

Verification

  1. Verify that your system is prepared to be a virtualization host. Run the following command as root: 

    # virt-host-validate
[...]
QEMU: Checking if device /dev/vhost-net exists              : PASS
QEMU: Checking if device /dev/net/tun exists                : PASS
QEMU: Checking for cgroup 'memory' controller support       : PASS
QEMU: Checking for cgroup 'memory' controller mount-point   : PASS
[...]
QEMU: Checking for cgroup 'blkio' controller support        : PASS
QEMU: Checking for cgroup 'blkio' controller mount-point    : PASS
QEMU: Checking if IOMMU is enabled by kernel                : PASS

  2. If all virt-host-validate checks return a PASS value, your system is prepared for creating virtual machines.

    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.

Before using the RHEL 10 web console to manage virtual machines (VMs), you must install the web console virtual machine plugin on the host.

Prerequisites

Procedure

  • Install the cockpit-machines plugin. 

    # dnf install cockpit-machines

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.

When managing virtual machines (VMs) on a remote host system by using libvirt utilities on the command line, you can optimize the process of connecting to the remote host.

By default, to connect to a VM on a remote host, you must use the -c qemu+ssh://root@hostname/system syntax. For example, to use the virsh list command as root on the 192.0.2.1 host: 

# virsh -c qemu+ssh://root@192.0.2.1/system list

Example output: 

root@192.0.2.1's password:

Id   Name              State
---------------------------------
1    remote-guest      running

However, you can remove the need to specify the connection details in full by modifying your SSH and libvirt configuration. For example: 

# virsh -c remote-host list

Example output: 

root@192.0.2.1's password:

Id   Name              State
---------------------------------
1    remote-guest      running

To enable this improvement, use the following instructions.

Prerequisites

Procedure

  1. Edit the ~/.ssh/config file on your local host and add an entry similar to the following: 

    Host <host-alias>
  User                    root
  Hostname                192.0.2.1

    In this example, <host-alias> is a shortened name associated with the root@192.0.2.1 remote host connection.

  2. Edit the /etc/libvirt/libvirt.conf file and add lines similar to the following: 

    uri_aliases = [
  "<qemu-alias>=qemu+ssh://<host-alias>/system",
]

    In this example, <qemu-alias> is a host alias that QEMU and libvirt utilities will use for the qemu+ssh://192.0.2.1/system connection.

  3. Optional: If you want to use libvirt utilities exclusively on a single remote host, you can also set a specific connection as the default target for libvirt-based utilities.

    Edit the /etc/libvirt/libvirt.conf file and set the value of the uri_default parameter to <qemu-alias> as a default libvirt target. 

    # These can be used in cases when no URI is supplied by the application
# (@uri_default also prevents probing of the hypervisor driver).
#
uri_default = "<qemu-alias>"
    Warning

    You cannot do this if you also want to manage VMs on your local host or on different remote hosts.

  4. Optional: To avoid having to provide the root password when connecting to a remote host, use one or more of the following methods:

Verification

  1. Confirm that you can manage remote VMs by using libvirt-based utilities on the local system with an added -c <qemu-alias> parameter. This automatically performs the commands over SSH on the remote host.

    For example, verify that the following lists VMs on the 192.0.2.1 remote host, the connection to which was set up as <qemu-alias> in the previous steps: 

    # virsh -c <qemu-alias> list

    Successful output: 

    root@192.0.2.1's password:

Id   Name                       State
----------------------------------------
1    example-remote-guest      running

  2. If you have set up the default URI to a remote host, ensure that libvirt commands automatically apply to the specified remote host. 

    $ virsh list

    Successful output: 

    root@192.0.2.1's password:

Id   Name              State
---------------------------------
1   example-remote-guest      running
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