KVM
HypervisorKernel-based Virtual Machine: the type-1 hypervisor built into the Linux kernel. The foundation almost every Linux virtualization platform builds on.
linux-kvm.orgvirt-what(1) — shell command
Are you running on bare metal — or inside a virtual machine?
virt-what is a small shell script that answers exactly that question. This site explains the command and collects the open-source projects that make virtualization happen.
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NAME
virt-what — detect if we are running in a virtual machine
DESCRIPTION
virt-what is a shell script written by Richard W.M. Jones, maintained as part of the libguestfs tool family. Run inside a guest, it prints one or more facts describing the virtualization technology it detects — one per line — and prints nothing at all on bare metal.
Detection is based on low-level evidence: CPUID hypervisor leaves, DMI/SMBIOS strings, devices typical for a given hypervisor, and files under /proc and /sys. Because some of these sources are only readable by root, the script should be run with root privileges — otherwise results may be incomplete.
kvmLinux KVM — used by Proxmox VE, libvirt, OpenStack and most Linux hostsvmwareVMware ESXi / Workstation guesthypervMicrosoft Hyper-V (also the basis of many Azure VMs)xen / xen-hvmXen guest, paravirtualized or fully virtualizedlxcLinux container (LXC / Incus system container)(no output)No virtualization detected — physical hardwareTypical use: in Ansible facts, kickstart/cloud-init scripts or monitoring checks, where behavior should differ between physical and virtual machines.
OPEN-SOURCE VIRTUALIZATION
A curated, non-exhaustive list of open-source projects across the stack — from hypervisor to management platform.
QEMU
Emulator / VMMMachine emulator and virtualizer. Together with KVM it provides full hardware virtualization; on its own it can emulate foreign CPU architectures (x86 ↔ ARM, RISC-V …).
qemu.orglibvirt
API / ToolingUniform management API and daemon for KVM/QEMU, Xen, LXC and more. The layer behind virsh, virt-manager and many higher-level platforms.
libvirt.orgProxmox VE
PlatformComplete virtualization platform on Debian: KVM VMs plus LXC containers, clustering, HA, software-defined storage (ZFS, Ceph) and backups behind one web UI.
proxmox.comIncus
PlatformCommunity-driven fork of LXD: manages system containers and KVM virtual machines with one consistent CLI and REST API. Image-based, cluster-capable, lightweight.
linuxcontainers.org/incusXen Project
HypervisorVeteran type-1 hypervisor with a strong isolation model (dom0/domU). Powers Qubes OS and parts of large cloud infrastructure.
xenproject.orgLXC
ContainerLinux system containers: OS-level virtualization using namespaces and cgroups. Feels like a VM, shares the host kernel — the technology behind Proxmox containers and Incus.
linuxcontainers.orgFirecracker
MicroVMMinimal VMM in Rust, built by AWS for Lambda/Fargate. Boots stripped-down microVMs in milliseconds — strong isolation with container-like density.
firecracker-microvm.github.ioCloud Hypervisor
MicroVMModern Rust VMM under the Linux Foundation, focused on cloud workloads: minimal device model, virtio, strong security posture.
cloudhypervisor.orgKubeVirt
KubernetesRuns classic virtual machines as Kubernetes resources — VMs and containers side by side in the same cluster, managed with kubectl.
kubevirt.ioHarvester
HCIHyper-converged infrastructure by SUSE/Rancher: KubeVirt + Longhorn storage on Kubernetes, packaged as an installable appliance.
harvesterhci.ioVirtualBox
DesktopCross-platform type-2 hypervisor for the desktop (GPLv3 base package). Handy for quickly trying out operating systems on Linux, Windows and macOS.
virtualbox.orgCOMMANDS WORTH KNOWING
A handful of commands every virtualization admin reaches for sooner or later.
sudo virt-whatPrints the detected virtualization facts, e.g. kvm. No output means bare metal. Run as root for complete results.
systemd-detect-virtThe systemd alternative — present on virtually every modern distro. Returns e.g. kvm, lxc or none; --container and --vm narrow the check. Exit code 0 means “virtualized”, ideal for shell scripts.
lscpu | grep -i virtualizationOn a host: shows whether the CPU offers hardware virtualization (VT-x / AMD-V). In a guest it shows the hypervisor vendor instead.
sudo dmidecode -s system-product-nameReads the SMBIOS product string — virtual machines reveal themselves here with values like KVM, VMware Virtual Platform or Virtual Machine.
virsh list --alllibvirt's CLI: lists all defined VMs including stopped ones. virsh start, virsh shutdown and virsh console cover day-to-day operations.
qemu-img convert -O qcow2 disk.vmdk disk.qcow2Converts disk images between formats (vmdk, vdi, raw, qcow2) — the standard move when migrating VMs from VMware or VirtualBox to KVM.
qm list && pct listOn a Proxmox VE node: qm manages KVM VMs, pct manages LXC containers — start, stop, config, migrate, all scriptable.
incus launch images:debian/13 web1Creates and starts a Debian 13 system container in seconds. Add --vm and Incus launches a real KVM virtual machine from the same image server.