Virtual Machines & Containers

This article covers various virtualization and system container technologies available on Ubuntu 26.04.

Check Hardware Virtualization Support

Before getting started, confirm that your CPU supports hardware virtualization:


# Check for virtualization support
egrep -c '(vmx|svm)' /proc/cpuinfo

A result greater than 0 indicates support. You can also use cpu-checker:


sudo apt install cpu-checker -y
kvm-ok

KVM / QEMU

KVM (Kernel-based Virtual Machine) is a virtualization solution built into the Linux kernel. Combined with QEMU, it provides full virtualization capabilities.


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

Add the current user to the required groups:


sudo usermod -aG libvirt $USER
sudo usermod -aG kvm $USER

Log out and back in for the group changes to take effect.

Verify Installation


# Check libvirt service status
sudo systemctl status libvirtd
 
# Verify connection
virsh list --all

Using virt-manager (GUI)


virt-manager

virt-manager provides an intuitive graphical interface for creating and managing virtual machines.

Create a VM via Command Line


# Create a disk image
qemu-img create -f qcow2 /var/lib/libvirt/images/ubuntu-vm.qcow2 40G
 
# Install a VM from ISO
virt-install \
  --name ubuntu-vm \
  --ram 4096 \
  --vcpus 2 \
  --disk path=/var/lib/libvirt/images/ubuntu-vm.qcow2,size=40 \
  --os-variant ubuntu26.04 \
  --network bridge=virbr0 \
  --graphics vnc \
  --cdrom /path/to/ubuntu-26.04-desktop-amd64.iso

Note

Run osinfo-query os | grep ubuntu to confirm whether your local osinfo-db includes ubuntu26.04. If not, upgrade osinfo-db, fall back to the closest ubuntu24.04, or use --osinfo detect=on,require=off to let virt-install auto-detect.

Common virsh Commands


# List all VMs
virsh list --all
 
# Start a VM
virsh start ubuntu-vm
 
# Shut down a VM
virsh shutdown ubuntu-vm
 
# Force stop
virsh destroy ubuntu-vm
 
# Suspend and resume
virsh suspend ubuntu-vm
virsh resume ubuntu-vm
 
# Create snapshots
virsh snapshot-create-as ubuntu-vm --name "clean-install"
virsh snapshot-list ubuntu-vm
virsh snapshot-revert ubuntu-vm --snapshotname "clean-install"
 
# Delete a VM
virsh undefine ubuntu-vm --remove-all-storage

Using QEMU Directly

Without libvirt, using QEMU directly:


# Create a disk
qemu-img create -f qcow2 disk.qcow2 20G
 
# Start a VM
qemu-system-x86_64 \
  -enable-kvm \
  -m 4G \
  -smp 2 \
  -hda disk.qcow2 \
  -cdrom ubuntu.iso \
  -boot d \
  -net nic -net user,hostfwd=tcp::2222-:22

VirtualBox

VirtualBox is Oracle’s open-source virtualization software with a clean graphical interface.

Install VirtualBox


# Method 1: Install from Ubuntu repository
sudo apt install virtualbox -y
 
# Method 2: Install from Oracle's official repository (newer version)
wget -qO- https://www.virtualbox.org/download/oracle_vbox_2016.asc | sudo gpg --dearmor -o /etc/apt/keyrings/oracle-virtualbox.gpg
 
echo "deb [arch=amd64 signed-by=/etc/apt/keyrings/oracle-virtualbox.gpg] https://download.virtualbox.org/virtualbox/debian $(lsb_release -cs) contrib" | sudo tee /etc/apt/sources.list.d/virtualbox.list
 
sudo apt update
 
# Install VirtualBox (run apt-cache search virtualbox to confirm the current
# available package name, e.g. virtualbox-7.1 or a newer version)
sudo apt install virtualbox-7.1 -y

Install Extension Pack

The Extension Pack provides USB 3.0, RDP remote desktop, and other features:


# Install the extension pack after downloading the matching version
sudo VBoxManage extpack install Oracle_VirtualBox_Extension_Pack-*.vbox-extpack

VBoxManage Command Line


# List VMs
VBoxManage list vms
 
# Start a VM (headless mode)
VBoxManage startvm "vm-name" --type headless
 
# Shut down a VM
VBoxManage controlvm "vm-name" acpipowerbutton
 
# Create a snapshot
VBoxManage snapshot "vm-name" take "snapshot-name"

LXD / LXC System Containers

LXC is a Linux container technology, and LXD is its management daemon, providing a VM-like experience but more lightweight.

Install LXD


sudo snap install lxd

Initialize LXD


lxd init --minimal

Or use interactive configuration for more options:


lxd init

LXD Basic Operations


# Launch an Ubuntu container
lxc launch ubuntu:26.04 mycontainer
 
# Launch a VM (yes, LXD supports VMs too)
lxc launch ubuntu:26.04 myvm --vm
 
# List instances
lxc list
 
# Enter a container
lxc exec mycontainer -- bash
 
# Push and pull files
lxc file push local-file.txt mycontainer/root/
lxc file pull mycontainer/root/file.txt .
 
# Stop and delete
lxc stop mycontainer
lxc delete mycontainer
 
# Create snapshots
lxc snapshot mycontainer snap0
lxc restore mycontainer snap0

LXD Profile Configuration


# View default profile
lxc profile show default
 
# Create a custom profile
lxc profile create dev-profile
lxc profile set dev-profile limits.cpu 4
lxc profile set dev-profile limits.memory 8GB
 
# Launch a container with a custom profile
lxc launch ubuntu:26.04 devbox --profile dev-profile

Incus

Incus is a community fork of LXD, maintained by the Linux Containers community. It has similar functionality but is independently developed.

Install Incus


# Add the Zabbly repository (officially recommended for Incus)
curl -fsSL https://pkgs.zabbly.com/key.asc | sudo gpg --dearmor -o /etc/apt/keyrings/zabbly.gpg
 
echo "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/zabbly.gpg] https://pkgs.zabbly.com/incus/stable $(. /etc/os-release && echo "$VERSION_CODENAME") main" | sudo tee /etc/apt/sources.list.d/zabbly-incus-stable.list
 
sudo apt update
sudo apt install incus -y

Initialize and Use


# Initialize
sudo incus admin init --minimal
 
# Add user to the incus-admin group
sudo usermod -aG incus-admin $USER
newgrp incus-admin
 
# Usage is similar to LXD
incus launch images:ubuntu/26.04 mycontainer
incus list
incus exec mycontainer -- bash
incus stop mycontainer
incus delete mycontainer

Migrate from LXD to Incus


sudo incus admin migrate-lxd

Technology Comparison

Feature	KVM/QEMU	VirtualBox	LXD/Incus
Virtualization type	Full virtualization	Full virtualization	System containers/VMs
Performance	Near-native	Good	Near-native
Isolation	Strong	Strong	Medium (containers) / Strong (VMs)
Resource usage	Medium	Higher	Low (containers)
Use cases	Servers, production	Desktop dev/testing	Dev environments, lightweight isolation

Choose the right virtualization approach based on your use case: KVM for production servers, VirtualBox for desktop users, and LXD or Incus for development isolation environments.