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Chapter 2. Getting started with virtualization

To start using virtualization in RHEL 8, follow the steps below. The default method for this is using the command-line interface (CLI), but for user convenience, some of the steps can be completed in the web console GUI.

Note

The web console currently provides only a subset of VM management functions, so using the command line is recommended for advanced use of virtualization in RHEL 8.

2.1. Enabling virtualization

To use virtualization in RHEL 8, you must enable the virtualization module, install virtualization packages, and ensure your system is configured to host virtual machines (VMs).

Prerequisites

  • RHEL 8 is installed and registered on your host machine.
  • Your system meets the following hardware requirements to work as a virtualization host:

    • 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.
    • The architecture of your host machine supports KVM virtualization.

      • Notably, RHEL 8 does not support virtualization on the 64-bit ARM architecture (ARM 64).
      • The procedure below applies to the AMD64 and Intel 64 architecture (x86_64). To enable virtualization on a host with a different supported architecture, see one of the following sections:

Procedure

  1. Install the packages in the RHEL 8 virtualization module:

    # yum module install virt
  2. Install the virt-install and virt-viewer packages:

    # yum install virt-install virt-viewer
  3. Start the libvirtd service:

    # systemctl start libvirtd

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)
  2. Review the return values of virt-host-validate checks and take appropriate actions:

    1. If all virt-host-validate checks return the PASS value, your system is prepared for creating VMs.
    2. If any of the checks return a FAIL value, follow the displayed instructions to fix the problem.
    3. 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.

2.2. Creating virtual machines

To create a virtual machine (VM) in RHEL 8, use the command-line interface or the RHEL 8 web console.

2.2.1. Creating virtual machines by using the command-line interface

To create a virtual machine (VM) on your RHEL 8 host by using the virt-install utility, follow the instructions below.

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 may 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 8. If you select a CD-ROM or DVD-ROM as the installation source when using any VM installation method available in RHEL 8, the installation will fail. For more information, see the Red Hat Knowledgebase.

      Also note that Red Hat provides support only for a limited set of guest operating systems.

  • Optional: A Kickstart file can be provided for faster and easier configuration of the installation.

Procedure

To create a VM and start its OS installation, use the virt-install command, along with the following mandatory arguments:

  • --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

Based on the chosen installation method, the necessary options and values can vary. See the commands below for examples:

Note

The listed commands use the VNC remote display protocol instead of the default SPICE protocol. VNC currently does not have some of the features that SPICE does, but is fully supported on RHEL 9. As a result, VMs that use VNC will not stop working if you migrate your host to RHEL 9. For more information, see Considerations in adopting RHEL 9.

  • 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 \
        --graphics vnc \
        --name demo-guest1 --memory 2048 \
        --vcpus 2 --disk size=80 --os-variant win10 \
        --cdrom /home/username/Downloads/Win10install.iso
  • The following command creates a VM named demo-guest2 that uses the /home/username/Downloads/rhel8.iso image to run a RHEL 8 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 \
        --graphics vnc \
        --name demo-guest2 --memory 4096 --vcpus 4 \
        --disk none --livecd --os-variant rhel8.0 \
        --cdrom /home/username/Downloads/rhel8.iso
  • The following command creates a RHEL 8 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 \
        --graphics vnc \
        --name demo-guest3 --memory 2048 --vcpus 2 \
        --os-variant rhel8.0 --import \
        --disk /home/username/backup/disk.qcow2

    Note that the --os-variant option is highly recommended when importing a disk image. If it is not provided, the performance of the created VM will be negatively affected.

  • 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 \
        --graphics vnc \
        --name demo-guest4 --memory 2048 --vcpus 2 --disk size=160 \
        --os-variant rhel8.0 --location http://example.com/OS-install \
        --initrd-inject /home/username/ks.cfg --extra-args="inst.ks=file:/ks.cfg console=tty0 console=ttyS0,115200n8"
  • The following command creates a VM named demo-guest5 that installs from a RHEL8.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 \
        --os-variant rhel8.0 --location RHEL8.iso \
        --graphics none --extra-args='console=ttyS0'
  • 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 --os-variant rhel8.0 --location RHEL8.iso \
        --graphics none --extra-args='console=ttyS0'

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:

      # {PackageManagerCommand} info libvirt-daemon-config-network
      Installed Packages
      Name         : libvirt-daemon-config-network
      [...]
    • 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
    • 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
      • 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'

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

        # {PackageManagerCommand} reinstall libvirt-daemon-config-network
      • 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

        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.

2.2.2. Creating virtual machines and installing guest operating systems by using the web console

To manage virtual machines (VMs) in a GUI on a RHEL 8 host, use the web console. The following sections provide information about how to use the RHEL 8 web console to create VMs and install guest operating systems on them.

Important

VMs created by using the web console currently use the SPICE remote desktop protocol by default. However, SPICE is unsupported on RHEL 9, so if you upgrade your host to RHEL 9, the VM will stop working. For more information, see Considerations in adopting RHEL 9.

To create a VM that uses the VNC protocol, which will work correctly on RHEL 9, use the command-line interface.

2.2.2.1. Creating virtual machines by using the web console

To create a virtual machine (VM) on a host machine to which your RHEL 8 web console is connected, use the instructions below.

Prerequisites

Procedure

  1. In the Virtual Machines interface of the web console, click Create VM.

    The Create new virtual machine dialog appears.

    Image displaying the Create new virtual machine dialog box.
  2. Enter the basic configuration of the VM you want to create.

    • Name - The name of the VM.
    • Connection - The level of privileges granted to the session. For more details, expand the associated dialog box in the web console.
    • Installation type - The installation can use a local installation medium, a URL, a PXE network boot, a cloud base image, or download an operating system from a limited set of operating systems.
    • Operating system - The guest operating system running on the VM. Note that Red Hat provides support only for a limited set of guest operating systems.

      Note

      To download and install Red Hat Enterprise Linux directly from web console, you must add an offline token in the Offline token field.

    • Storage - The type of storage.
    • Storage Limit - The amount of storage space.
    • Memory - The amount of memory.
  3. Create the VM:

    • If you want the VM to automatically install the operating system, click Create and run.
    • If you want to edit the VM before the operating system is installed, click Create and edit.

2.2.2.2. Creating virtual machines by importing disk images by using the web console

You can create a virtual machine (VM) by importing a disk image of an existing VM installation in the RHEL 8 web console.

Prerequisites

  • The web console VM plug-in is installed on your system.
  • You have a sufficient amount of system resources to allocate to your VMs, such as disk space, RAM, or CPUs. The recommended values can vary significantly depending on the intended tasks and workload of the VMs.
  • You have downloaded a disk image of an existing VM installation.

Procedure

  1. In the Virtual Machines interface of the web console, click Import VM.

    The Import a virtual machine dialog appears.

    Image displaying the Import a virtual machine dialog box.
  2. Enter the basic configuration of the VM you want to create:

    • Name - The name of the VM.
    • Disk image - The path to the existing disk image of a VM on the host system.
    • Operating system - The operating system running on a VM disk. Note that Red Hat provides support only for a limited set of guest operating systems.
    • Memory - The amount of memory to allocate for use by the VM.
  3. Import the VM:

    • To install the operating system on the VM without additional edits to the VM settings, click Import and run.
    • To edit the VM settings before the installation of the operating system, click Import and edit.

2.2.2.3. Installing guest operating systems by using the web console

When a virtual machine (VM) boots for the first time, you must install an operating system on the VM.

Note

If you click Create and run or Import and run while creating a new VM, the installation routine for the operating system starts automatically when the VM is created.

Procedure

  1. In the Virtual Machines interface, click the VM on which you want to install a guest OS.

    A new page opens with basic information about the selected VM and controls for managing various aspects of the VM.

    Page displaying detailed information about the virtual machine.
  2. Optional: Change the firmware.

    Note

    You can change the firmware only if you selected Create and edit or Import and edit while creating a new VM and if the OS is not already installed on the VM.

    Image displaying the Change Firmware dialog box.
    1. Click the firmware.
    2. In the Change Firmware window, select the required firmware.
    3. Click Save.
  3. Click Install.

    The installation routine of the operating system runs in the VM console.

Troubleshooting

  • If the installation routine fails, delete and recreate the VM before starting the installation again.

2.2.3. Creating virtual machines with cloud image authentication by using the web console

By default, distro cloud images have no login accounts. However, by using the RHEL web console, you can now create a virtual machine (VM) and specify the root and user account login credentials, which are then passed to cloud-init.

Prerequisites

  • The web console VM plug-in is installed on your system.
  • 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 may vary significantly depending on the intended tasks and workload of the VMs.

Procedure

  1. In the Virtual Machines interface of the web console, click Create VM.

    The Create new virtual machine dialog appears.

    Image displaying the Create new virtual machine dialog box.
  2. In the Name field, enter a name for the VM.
  3. On the Details tab, in the Installation type field, select Cloud base image.

    Image displaying the Create new virtual machine by using cloud-init dialog box.
  4. In the Installation source field, set the path to the image file on your host system.
  5. Enter the configuration for the VM that you want to create.

    • Operating system - The VM’s operating system. Note that Red Hat provides support only for a limited set of guest operating systems.
    • Storage - The type of storage with which to configure the VM.
    • Storage Limit - The amount of storage space with which to configure the VM.
    • Memory - The amount of memory with which to configure the VM.
  6. Click on the Automation tab.

    Set your cloud authentication credentials.

    • Root password - Enter a root password for your VM. Leave the field blank if you do not wish to set a root password.
    • User login - Enter a cloud-init user login. Leave this field blank if you do not wish to create a user account.
    • User password - Enter a password. Leave this field blank if you do not wish to create a user account.

      Image displaying the Automation tab of the Create new virtual machine dialog box.
  7. Click Create and run.

    The VM is created.

2.3. Starting virtual machines

To start a virtual machine (VM) in RHEL 8, you can use the command line interface or the web console GUI.

Prerequisites

  • Before a VM can be started, it must be created and, ideally, also installed with an OS. For instruction to do so, see Creating virtual machines.

2.3.1. Starting a virtual machine by using the command-line interface

You can use the command line interface (CLI) to start a shut-down virtual machine (VM) or restore a saved VM. By using the CLI, you can start both local and remote VMs.

Prerequisites

  • An inactive VM that is already defined.
  • The name of the VM.
  • For remote VMs:

    • The IP address of the host where the VM is located.
    • Root access privileges to the host.

Procedure

  • For a local VM, use the virsh start utility.

    For example, the following command starts the demo-guest1 VM.

    # virsh start demo-guest1
    Domain 'demo-guest1' started
  • For a VM located on a remote host, use the virsh start utility along with the QEMU+SSH connection to the host.

    For example, the following command starts the demo-guest1 VM on the 192.0.2.1 host.

    # virsh -c qemu+ssh://root@192.0.2.1/system start demo-guest1
    
    root@192.0.2.1's password:
    
    Domain 'demo-guest1' started

2.3.2. Starting virtual machines by using the web console

If a virtual machine (VM) is in the shut off state, you can start it by using the RHEL 8 web console. You can also configure the VM to be started automatically when the host starts.

Prerequisites

Procedure

  1. In the Virtual Machines interface, click the VM you want to start.

    A new page opens with detailed information about the selected VM and controls for shutting down and deleting the VM.

  2. Click Run.

    The VM starts, and you can connect to its console or graphical output.

  3. Optional: To configure the VM to start automatically when the host starts, toggle the Autostart checkbox in the Overview section.

    If you use network interfaces that are not managed by libvirt, you must also make additional changes to the systemd configuration. Otherwise, the affected VMs might fail to start, see starting virtual machines automatically when the host starts.

2.3.3. Starting virtual machines automatically when the host starts

When a host with a running virtual machine (VM) restarts, the VM is shut down, and must be started again manually by default. To ensure a VM is active whenever its host is running, you can configure the VM to be started automatically.

Procedure

  1. Use the virsh autostart utility to configure the VM to start automatically when the host starts.

    For example, the following command configures the demo-guest1 VM to start automatically.

    # virsh autostart demo-guest1
    Domain 'demo-guest1' marked as autostarted
  2. If you use network interfaces that are not managed by libvirt, you must also make additional changes to the systemd configuration. Otherwise, the affected VMs might fail to start.

    Note

    These interfaces include for example:

    • Bridge devices created by NetworkManager
    • Networks configured to use <forward mode='bridge'/>
    1. In the systemd configuration directory tree, create a libvirtd.service.d directory if it does not exist yet.

      # mkdir -p /etc/systemd/system/libvirtd.service.d/
    2. Create a 10-network-online.conf systemd unit override file in the previously created directory. The content of this file overrides the default systemd configuration for the libvirtd service.

      # touch /etc/systemd/system/libvirtd.service.d/10-network-online.conf
    3. Add the following lines to the 10-network-online.conf file. This configuration change ensures systemd starts the libvirtd service only after the network on the host is ready.

      [Unit]
      After=network-online.target

Verification

  1. View the VM configuration, and check that the autostart option is enabled.

    For example, the following command displays basic information about the demo-guest1 VM, including the autostart option.

    # virsh dominfo demo-guest1
    Id:             2
    Name:           demo-guest1
    UUID:           e46bc81c-74e2-406e-bd7a-67042bae80d1
    OS Type:        hvm
    State:          running
    CPU(s):         2
    CPU time:       385.9s
    Max memory:     4194304 KiB
    Used memory:    4194304 KiB
    Persistent:     yes
    Autostart:      enable
    Managed save:   no
    Security model: selinux
    Security DOI:   0
    Security label: system_u:system_r:svirt_t:s0:c873,c919 (enforcing)
  2. If you use network interfaces that are not managed by libvirt, check if the content of the 10-network-online.conf file matches the following output.

    $ cat /etc/systemd/system/libvirtd.service.d/10-network-online.conf
    [Unit]
    After=network-online.target

Additional resources

2.4. Connecting to virtual machines

To interact with a virtual machine (VM) in RHEL 8, you need to connect to it by doing one of the following:

If the VMs to which you are connecting are on a remote host rather than a local one, you can optionally configure your system for more convenient access to remote hosts.

Prerequisites

2.4.1. Interacting with virtual machines by using the web console

To interact with a virtual machine (VM) in the RHEL 8 web console, you need to connect to the VM’s console. These include both graphical and serial consoles.

2.4.1.1. Viewing the virtual machine graphical console in the web console

By using the virtual machine (VM) console interface, you can view the graphical output of a selected VM in the RHEL 8 web console.

Prerequisites

Procedure

  1. In the Virtual Machines interface, click the VM whose graphical console you want to view.

    A new page opens with an Overview and a Console section for the VM.

  2. Select VNC console in the console drop down menu.

    The VNC console appears below the menu in the web interface.

    The graphical console appears in the web interface.

    Image displaying the interface of the selected virtual machine.
  3. Click Expand

    You can now interact with the VM console by using the mouse and keyboard in the same manner you interact with a real machine. The display in the VM console reflects the activities being performed on the VM.

Note

The host on which the web console is running may intercept specific key combinations, such as Ctrl+Alt+Del, preventing them from being sent to the VM.

To send such key combinations, click the Send key menu and select the key sequence to send.

For example, to send the Ctrl+Alt+Del combination to the VM, click the Send key and select the Ctrl+Alt+Del menu entry.

Troubleshooting

  • If clicking in the graphical console does not have any effect, expand the console to full screen. This is a known issue with the mouse cursor offset.

2.4.1.2. Viewing the graphical console in a remote viewer by using the web console

By using the web console interface, you can display the graphical console of a selected virtual machine (VM) in a remote viewer, such as Virt Viewer.

Note

You can launch Virt Viewer from within the web console. Other VNC and SPICE remote viewers can be launched manually.

Prerequisites

  • The web console VM plug-in is installed on your system.
  • Ensure that both the host and the VM support a graphical interface.
  • Before you can view the graphical console in Virt Viewer, you must install Virt Viewer on the machine to which the web console is connected.

    1. Click Launch remote viewer.

      The virt viewer, .vv, file downloads.

    2. Open the file to launch Virt Viewer.
Note

Remote Viewer is available on most operating systems. However, some browser extensions and plug-ins do not allow the web console to open Virt Viewer.

Procedure

  1. In the Virtual Machines interface, click the VM whose graphical console you want to view.

    A new page opens with an Overview and a Console section for the VM.

  2. Select Desktop Viewer in the console drop down menu.

    Page displaying the Console section of the virtual machine interface along with other VM details.
  3. Click Launch Remote Viewer.

    The graphical console opens in Virt Viewer.

    You can interact with the VM console by using the mouse and keyboard in the same manner in which you interact with a real machine. The display in the VM console reflects the activities being performed on the VM.

Note

The server on which the web console is running can intercept specific key combinations, such as Ctrl+Alt+Del, preventing them from being sent to the VM.

To send such key combinations, click the Send key menu and select the key sequence to send.

For example, to send the Ctrl+Alt+Del combination to the VM, click the Send key menu and select the Ctrl+Alt+Del menu entry.

Troubleshooting

  • If clicking in the graphical console does not have any effect, expand the console to full screen. This is a known issue with the mouse cursor offset.
  • If launching the Remote Viewer in the web console does not work or is not optimal, you can manually connect with any viewer application by using the following protocols:

    • Address - The default address is 127.0.0.1. You can modify the vnc_listen or the spice_listen parameter in /etc/libvirt/qemu.conf to change it to the host’s IP address.
    • SPICE port - 5900
    • VNC port - 5901

2.4.1.3. Viewing the virtual machine serial console in the web console

You can view the serial console of a selected virtual machine (VM) in the RHEL 8 web console. This is useful when the host machine or the VM is not configured with a graphical interface.

For more information about the serial console, see Opening a virtual machine serial console.

Prerequisites

Procedure

  1. In the Virtual Machines pane, click the VM whose serial console you want to view.

    A new page opens with an Overview and a Console section for the VM.

  2. Select Serial console in the console drop down menu.

    The graphical console appears in the web interface.

    Page displaying the virtual machine serial console along with other VM details.

You can disconnect and reconnect the serial console from the VM.

  • To disconnect the serial console from the VM, click Disconnect.
  • To reconnect the serial console to the VM, click Reconnect.

2.4.2. Opening a virtual machine graphical console by using Virt Viewer

To connect to a graphical console of a KVM virtual machine (VM) and open it in the Virt Viewer desktop application, follow the procedure below.

Prerequisites

  • Your system, as well as the VM you are connecting to, must support graphical displays.
  • If the target VM is located on a remote host, connection and root access privileges to the host are needed.
  • Optional: If the target VM is located on a remote host, set up your libvirt and SSH for more convenient access to remote hosts.

Procedure

  • To connect to a local VM, use the following command and replace guest-name with the name of the VM you want to connect to:

    # virt-viewer guest-name
  • To connect to a remote VM, use the virt-viewer command with the SSH protocol. For example, the following command connects as root to a VM called guest-name, located on remote system 192.0.2.1. The connection also requires root authentication for 192.0.2.1.

    # virt-viewer --direct --connect qemu+ssh://root@192.0.2.1/system guest-name
    root@192.0.2.1's password:

Verification

If the connection works correctly, the VM display is shown in the Virt Viewer window.

You can interact with the VM console by using the mouse and keyboard in the same manner you interact with a real machine. The display in the VM console reflects the activities being performed on the VM.

Troubleshooting

  • If clicking in the graphical console does not have any effect, expand the console to full screen. This is a known issue with the mouse cursor offset.

2.4.3. Connecting to a virtual machine by using SSH

To interact with the terminal of a virtual machine (VM) by using the SSH connection protocol, follow the procedure below.

Prerequisites

  • You have network connection and root access privileges to the target VM.
  • If the target VM is located on a remote host, you also have connection and root access privileges to that host.
  • Your VM network assigns IP addresses by dnsmasq generated by libvirt. This is the case for example in libvirt NAT networks.

    Notably, if your VM is using one of the following network configurations, you cannot connect to the VM by using SSH:

    • hostdev interfaces
    • Direct interfaces
    • Bridge interaces
  • The libvirt-nss component is installed and enabled on the VM’s host. If it is not, do the following:

    1. Install the libvirt-nss package:

      # yum install libvirt-nss
    2. Edit the /etc/nsswitch.conf file and add libvirt_guest to the hosts line:

      ...
      passwd:      compat
      shadow:      compat
      group:       compat
      hosts:       files libvirt_guest dns
      ...

Procedure

  1. When connecting to a remote VM, SSH into its physical host first. The following example demonstrates connecting to a host machine 192.0.2.1 by using its root credentials:

    # ssh root@192.0.2.1
    root@192.0.2.1's password:
    Last login: Mon Sep 24 12:05:36 2021
    root~#
  2. Use the VM’s name and user access credentials to connect to it. For example, the following connects to to the testguest1 VM by using its root credentials:

    # ssh root@testguest1
    root@testguest1's password:
    Last login: Wed Sep 12 12:05:36 2018
    root~]#

Troubleshooting

  • If you do not know the VM’s name, you can list all VMs available on the host by using the virsh list --all command:

    # virsh list --all
    Id    Name                           State
    ----------------------------------------------------
    2     testguest1                    running
    -     testguest2                    shut off

Additional resources

2.4.4. Opening a virtual machine serial console

By using the virsh console command, it is possible to connect to the serial console of a virtual machine (VM).

This is useful when the VM:

  • Does not provide VNC or SPICE protocols, and thus does not offer video display for GUI tools.
  • Does not have a network connection, and thus cannot be interacted with using SSH.

Prerequisites

  • The VM must have a serial console device configured, such as console type='pty'. To verify, do the following:

    # virsh dumpxml vm-name | grep console
    
    <console type='pty' tty='/dev/pts/2'>
    </console>
  • The VM must have the serial console configured in its kernel command line. To verify this, the cat /proc/cmdline command output on the VM should include console=ttyS0. For example:

    # cat /proc/cmdline
    BOOT_IMAGE=/vmlinuz-3.10.0-948.el7.x86_64 root=/dev/mapper/rhel-root ro console=tty0 console=ttyS0,9600n8 rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap rhgb

    If the serial console is not set up properly on a VM, using virsh console to connect to the VM connects you to an unresponsive guest console. However, you can still exit the unresponsive console by using the Ctrl+] shortcut.

    • To set up serial console on the VM, do the following:

      1. On the VM, enable the console=ttyS0 kernel option:

        # grubby --update-kernel=ALL --args="console=ttyS0"
      2. Clear the kernel options that might prevent your changes from taking effect.

        # grub2-editenv - unset kernelopts
      3. Reboot the VM.

Procedure

  1. On your host system, use the virsh console command. The following example connects to the guest1 VM, if the libvirt driver supports safe console handling:

    # virsh console guest1 --safe
    Connected to domain 'guest1'
    Escape character is ^]
    
    Subscription-name
    Kernel 3.10.0-948.el7.x86_64 on an x86_64
    
    localhost login:
  2. You can interact with the virsh console in the same way as with a standard command-line interface.

Additional resources

  • The virsh man page

2.4.5. Setting up easy access to remote virtualization hosts

When managing VMs on a remote host system by using libvirt utilities, it is recommended to 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
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
root@192.0.2.1's password:

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

To enable this improvement, follow the instructions below.

Procedure

  1. Edit the ~/.ssh/config file with the following details, where host-alias is a shortened name associated with a specific remote host and an alias for root@192.0.2.1, and hosturl is the URL address of the host :

    # vi ~/.ssh/config
    Host example-host-alias
      User                    root
      Hostname                192.0.2.1
  2. Edit the /etc/libvirt/libvirt.conf file with the following details, the example-qemu-host-alias is a host alias that QEMU and libvirt utilities will associate for qemu+ssh://192.0.2.1/system with the intended host example-host-alias :

    # vi /etc/libvirt/libvirt.conf
    uri_aliases = [
      "example-qemu-host-alias=qemu+ssh://example-host-alias/system",
    ]

Verification

  1. Confirm that you can manage remote VMs by using libvirt-based utilities on the local system with an added -c qemu-host-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 example-qemu-host-alias in the previous steps:

    # virsh -c example-qemu-host-alias list
    
    root@192.0.2.1's password:
    
    Id   Name                       State
    ----------------------------------------
    1    example-remote-guest      running
    Note

    In addition to virsh, the -c (or --connect) option and the remote host access configuration described above can be used by the following utilities:

Next steps

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. However, this is not recommended if you also want to manage VMs on your local host or on different remote hosts.

  • You can edit the /etc/libvirt/libvirt.conf file and set the value of the uri_default parameter to example-qemu-host-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 = "example-qemu-host-alias"

    As a result, all libvirt-based commands will automatically be performed on the specified remote host.

    $ virsh list
    root@192.0.2.1's password:
    
    Id   Name              State
    ---------------------------------
    1   example-remote-guest      running
  • When connecting to a remote host, you can avoid providing the root password to the remote system. To do so, use one or more of the following methods:

  • The -c (or --connect) option can be used to run the virt-install, virt-viewer, virsh and virt-manager commands on a remote host.

2.5. Shutting down virtual machines

To shut down a running virtual machine hosted on RHEL 8, use the command line interface or the web console GUI.

2.5.1. Shutting down a virtual machine by using the command-line interface

To shut down a responsive virtual machine (VM), do one of the following:

  • Use a shutdown command appropriate to the guest OS while connected to the guest.
  • Use the virsh shutdown command on the host:

    • If the VM is on a local host:

      # virsh shutdown demo-guest1
      Domain 'demo-guest1' is being shutdown
    • If the VM is on a remote host, in this example 192.0.2.1:

      # virsh -c qemu+ssh://root@192.0.2.1/system shutdown demo-guest1
      
      root@192.0.2.1's password:
      Domain 'demo-guest1' is being shutdown

To force a VM to shut down, for example if it has become unresponsive, use the virsh destroy command on the host:

# virsh destroy demo-guest1
Domain 'demo-guest1' destroyed
Note

The virsh destroy command does not actually delete or remove the VM configuration or disk images. It only terminates the running VM instance of the VM, similarly to pulling the power cord from a physical machine. As such, in rare cases, virsh destroy may cause corruption of the VM’s file system, so using this command is only recommended if all other shutdown methods have failed.

2.5.2. Shutting down and restarting virtual machines by using the web console

Using the RHEL 8 web console, you can shut down or restart running virtual machines. You can also send a non-maskable interrupt to an unresponsive virtual machine.

2.5.2.1. Shutting down virtual machines in the web console

If a virtual machine (VM) is in the running state, you can shut it down by using the RHEL 8 web console.

Prerequisites

Procedure

  1. In the Virtual Machines interface, find the row of the VM you want to shut down.
  2. On the right side of the row, click Shut Down.

    The VM shuts down.

Troubleshooting

  • If the VM does not shut down, click the Menu button next to the Shut Down button and select Force Shut Down.
  • To shut down an unresponsive VM, you can also send a non-maskable interrupt.

2.5.2.2. Restarting virtual machines by using the web console

If a virtual machine (VM) is in the running state, you can restart it by using the RHEL 8 web console.

Prerequisites

Procedure

  1. In the Virtual Machines interface, find the row of the VM you want to restart.
  2. On the right side of the row, click the Menu button .

    A drop-down menu of actions appears.

  3. In the drop-down menu, click Reboot.

    The VM shuts down and restarts.

Troubleshooting

  • If the VM does not restart, click the Menu button next to the Reboot button and select Force Reboot.
  • To shut down an unresponsive VM, you can also send a non-maskable interrupt.

2.5.2.3. Sending non-maskable interrupts to VMs by using the web console

Sending a non-maskable interrupt (NMI) may cause an unresponsive running virtual machine (VM) to respond or shut down. For example, you can send the Ctrl+Alt+Del NMI to a VM that is not responding to standard input.

Prerequisites

Procedure

  1. In the Virtual Machines interface, find the row of the VM to which you want to send an NMI.
  2. On the right side of the row, click the Menu button .

    A drop-down menu of actions appears.

  3. In the drop-down menu, click Send non-maskable interrupt.

    An NMI is sent to the VM.

2.6. Deleting virtual machines

To delete virtual machines in RHEL 8, use the command line interface or the web console GUI.

2.6.1. Deleting virtual machines by using the command line interface

To delete a virtual machine (VM), you can remove its XML configuration and associated storage files from the host by using the command line. Follow the procedure below:

Prerequisites

  • Back up important data from the VM.
  • Shut down the VM.
  • Make sure no other VMs use the same associated storage.

Procedure

  • Use the virsh undefine utility.

    For example, the following command removes the guest1 VM, its associated storage volumes, and non-volatile RAM, if any.

    # virsh undefine guest1 --remove-all-storage --nvram
    Domain 'guest1' has been undefined
    Volume 'vda'(/home/images/guest1.qcow2) removed.

Additional resources

  • The virsh undefine --help command
  • The virsh man page

2.6.2. Deleting virtual machines by using the web console

To delete a virtual machine (VM) and its associated storage files from the host to which the RHEL 8 web console is connected with, follow the procedure below:

Prerequisites

  • The web console VM plug-in is installed on your system.
  • Back up important data from the VM.
  • Make sure no other VM uses the same associated storage.
  • Optional: Shut down the VM.

Procedure

  1. In the Virtual Machines interface, click the Menu button of the VM that you want to delete.

    A drop down menu appears with controls for various VM operations.

  2. Click Delete.

    A confirmation dialog appears.

    Image displaying the Confirm deletion of VM dialog box.
  3. Optional: To delete all or some of the storage files associated with the VM, select the checkboxes next to the storage files you want to delete.
  4. Click Delete.

    The VM and any selected storage files are deleted.