KVM (Kernel-based Virtual Machine) is a powerful open-source virtualization technology built directly into the Linux kernel. If you need to run virtual machines on your Ubuntu system, understanding how to install KVM on Ubuntu 26.04 is essential for both development and production environments. This guide walks you through the complete KVM install process on Ubuntu 26.04, from verifying hardware support to creating your first virtual machine.

Software Requirements

Virtualization Options on Ubuntu 26.04

Ubuntu 26.04 supports several virtualization solutions, each with different strengths. KVM stands out as the recommended choice for Linux users because it integrates directly into the kernel, delivering near-native performance without additional licensing costs. The following table compares the available options to help you choose the right solution for your needs.

Prerequisites for KVM Install on Ubuntu 26.04

Before installing KVM, you must verify that your CPU supports hardware virtualization. Modern Intel processors include VT-x technology, while AMD processors include AMD-V. Without these extensions enabled, KVM cannot function properly.

1. Check CPU virtualization support: Run the following command to verify your processor supports virtualization extensions:

   $ egrep -c '(vmx|svm)' /proc/cpuinfo

   A result greater than 0 indicates your CPU supports virtualization. The output shows the number of CPU cores with virtualization capability. If you see 0, you need to enable virtualization in your BIOS/UEFI settings.

2. Verify KVM module availability: Install the cpu-checker package and run kvm-ok to confirm your system can run KVM:

   $ sudo apt install cpu-checker
   $ kvm-ok

   A successful output shows “KVM acceleration can be used”. If KVM cannot be used, verify virtualization is enabled in your BIOS/UEFI settings.

Install KVM Packages on Ubuntu 26.04

Ubuntu 26.04 provides all necessary KVM components through its official repositories. The installation includes QEMU as the machine emulator, libvirt for managing virtual machines, and virt-manager for a graphical interface. If you prefer working with QEMU-KVM directly from the command line, the same packages apply.

1. Update the package index: Ensure your package lists are current before installing:

   $ sudo apt update

2. Install the KVM virtualization stack: Install all required packages with a single command:

   $ sudo apt install qemu-kvm libvirt-daemon-system libvirt-clients bridge-utils virt-manager

   This command installs:

   • qemu-kvm – The QEMU emulator with KVM support
   • libvirt-daemon-system – The libvirt daemon and system configuration
   • libvirt-clients – Command-line utilities for managing VMs
   • bridge-utils – Utilities for configuring network bridges
   • virt-manager – Graphical VM management application
3. Verify the libvirt service is running: The libvirtd service should start automatically after installation:

   $ sudo systemctl status libvirtd

   You should see “active (running)” in the output. If the service shows “inactive (dead)” with an error like User record for user 'libvirt-qemu' was not found, this is a timing issue during installation. Simply restart the service:

   $ sudo systemctl restart libvirtd

   If the service is not enabled, enable it with:

   $ sudo systemctl enable --now libvirtd

Configure User Permissions for KVM

By default, only root can manage virtual machines. To use KVM as a regular user, you must add your account to the libvirt and kvm groups. This step is essential for running virt-manager without requiring sudo.

1. Add your user to the required groups: Execute the following command to grant your user access to KVM:

   $ sudo usermod -aG libvirt,kvm $USER

   The -aG flag appends these groups without removing existing group memberships.

2. Apply the group changes: Log out and log back in for the group membership to take effect. Alternatively, use the newgrp command to apply changes in the current session:

   $ newgrp libvirt

3. Verify group membership: Confirm your user belongs to the correct groups:

   $ groups

   The output should include both libvirt and kvm in the list.

   👁 Terminal showing usermod command adding user to libvirt and kvm groups, followed by newgrp and groups command confirming libvirt membership
   

Verify KVM Installation on Ubuntu 26.04

After completing the installation and configuring permissions, verify that KVM is working correctly. These verification steps confirm that both the kernel modules and the libvirt management layer function properly.

1. Check KVM kernel modules: Verify the KVM modules are loaded in the kernel:

   $ lsmod | grep kvm
   kvm_intel 593920 0
   kvm 1495040 1 kvm_intel
   irqbypass 16384 1 kvm

   On AMD systems, you will see kvm_amd instead of kvm_intel.

2. Test libvirt connectivity: Verify you can connect to the libvirt daemon:

   $ virsh list --all
    Id Name State
   --------------------

   An empty list is normal for a fresh installation. If you receive a permission error, ensure you logged out and back in after adding group memberships.

3. Check the default network: Verify the default NAT network is available:

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

   If it shows as inactive, start it with:

   $ sudo virsh net-start default
   $ sudo virsh net-autostart default

Create Your First Virtual Machine

With KVM successfully installed, you can now create virtual machines. The virt-manager application provides an intuitive graphical interface for VM creation and management. For lightweight Ubuntu VMs, you might also consider Multipass as an alternative.

1. Launch virt-manager: Open the Virtual Machine Manager from your applications menu or run:

   $ virt-manager

2. Create a new virtual machine: Click the “Create a new virtual machine” button or select File > New Virtual Machine. The wizard guides you through selecting an installation source (ISO image, network install, or existing disk), allocating memory and CPU cores, and configuring storage.
3. Configure VM resources: For a basic Ubuntu guest, allocate at least 2 GB RAM and 2 CPU cores. Create a virtual disk of at least 25 GB for a comfortable installation.

For more information on KVM capabilities and advanced configuration options, consult the official Ubuntu virtualization documentation.

Conclusion

You have successfully completed the KVM install on Ubuntu 26.04. Your system is now ready to run virtual machines using the powerful KVM hypervisor integrated into the Linux kernel. The combination of QEMU, libvirt, and virt-manager provides a complete virtualization solution suitable for development, testing, and production workloads.

Frequently Asked Questions

1. How do I check if KVM is installed on Ubuntu 26.04? Run virsh list --all to verify KVM is installed and functioning. If the command returns a list (even empty), KVM is properly installed. You can also check for KVM kernel modules with lsmod | grep kvm.
2. Why does virt-manager show “Unable to connect to libvirt”? This error typically occurs when your user is not in the libvirt group or when the libvirtd service is not running. Add your user to the libvirt group with sudo usermod -aG libvirt $USER, log out and back in, then verify the service is running with sudo systemctl status libvirtd.
3. Can I run KVM inside a virtual machine (nested virtualization)? Yes, but nested virtualization must be enabled on the host. For Intel processors, check if nested virtualization is enabled with cat /sys/module/kvm_intel/parameters/nested. If it shows “N”, you need to enable it by adding options kvm_intel nested=1 to /etc/modprobe.d/kvm.conf and reloading the module.
4. What is the difference between KVM and VirtualBox? KVM is a Type-1 hypervisor integrated directly into the Linux kernel, offering near-native performance for Linux hosts. VirtualBox is a Type-2 hypervisor that runs as an application on top of the operating system. KVM generally provides better performance for Linux guests, while VirtualBox offers broader host OS support and may be easier to set up for beginners.