Chapter 1. Basic concepts of virtualization in RHEL

Next steps

• To start using virtualization in RHEL 10, see Preparing RHEL to host virtual machines.
• In addition to RHEL 10 virtualization, Red Hat offers a number of specialized virtualization solutions, each with a different user focus and features. For more information, see Red Hat virtualization solutions.

• Flexible and fine-grained allocation of resources

  A VM runs on a host machine, which is usually physical, and physical hardware can also be assigned for the guest OS to use. However, the allocation of physical resources to the VM is done on the software level, and is therefore very flexible. A VM uses a configurable fraction of the host memory, CPUs, or storage space, and that configuration can specify very fine-grained resource requests.

  For example, what the guest OS sees as its disk can be represented as a file on the host file system, and the size of that disk is less constrained than the available sizes for physical disks.

• Software-controlled configurations

  The entire configuration of a VM is saved as data on the host, and is under software control. Therefore, a VM can easily be created, removed, cloned, migrated, operated remotely, or connected to remote storage.

  In addition, the current state of the VM can be backed up as a snapshot at any time. A snapshot can then be loaded to restore the system to the saved state.

• Separation from the host

  A guest OS runs on a virtualized kernel, separate from the host OS. This means that any OS can be installed on a VM, and even if the guest OS becomes unstable or is compromised, the host is not affected in any way.

• Space and cost efficiency

  A single physical machine can host a large number of VMs. Therefore, it avoids the need for multiple physical machines to do the same tasks, and thus lowers the space, power, and maintenance requirements associated with physical hardware.

• Software compatibility

  Because a VM can use a different OS than its host, virtualization makes it possible to run applications that were not originally released for your host OS. For example, using a RHEL 8 guest OS, you can run applications released for RHEL 8 on a RHEL 10 host system.

• Metadata such as the name of the VM, time zone, and other information about the VM.
• A description of the devices in the VM, including virtual CPUs (vCPUS), storage devices, input/output devices, network interface cards, and other hardware, real and virtual.
• VM settings such as the maximum amount of memory it can use, restart settings, and other settings about the behavior of the VM.

• virsh - A versatile virtualization command-line utility and shell with a great variety of purposes, depending on the provided arguments. For example:

  • Starting and shutting down a VM - virsh start and virsh shutdown
  • Listing available VMs - virsh list
  • Creating a VM from a configuration file - virsh create
  • Entering a virtualization shell - virsh

  For more information, see the virsh(1) man page on your system.

• virt-install - A CLI utility for creating new VMs. For more information, see the virt-install(1) man page on your system.
• virt-xml - A utility for editing the configuration of a VM.
• guestfish - A utility for examining and modifying VM disk images. For more information, see the guestfish(1) man page on your system.

• The RHEL 10 web console, also known as Cockpit, provides a remotely accessible and easy to use graphical user interface for managing VMs and virtualization hosts.

• Advanced networking - You cannot set up system bridges or tap devices. You are limited to user-mode (passt) networking, and cannot configure full external visibility of the VM.
• PCI device passthrough - Modifying the device assignment of PCI host hardware for the VM is not possible.
• Autostart - VMs in the session connection cannot automatically start on system boot.
• System-level storage pools and VM logs - In the system connection, storage pools and VM log files are saved in system directories, such as /etc/libvirt and /var/lib/libvirt. In the session connection, the user is limited to files saved in their home directory. This prevents managing host-wide storage or viewing logs centrally.