libvirt / virt-manager

April 18, 2026 · View on GitHub

libvirt is a toolkit to manage virtual machines and accompanying virtual storage, networking, and more. libvirt allows easy and comprehensive management of KVM/QEMU virtual machines through graphical (virt-manager) and command-line (virsh) interfaces.

Advantages of virtualization include:

Run many independent operating systems/environmnents on a single physical machine
Quickly create, clone and delete virtual machines for temporary/testing environments or horizontal scaling
VM operating systems are strongly isolated from each other and from the hypervisor
Easy, dynamic management of resources, virtual storage, RAM, CPU... (vertical scaling)
Easy rollback: snapshot the state of a VM, make changes, then restore the snapshot to return to the previous state
Create simple or complex virtual networks with routing, switching, firewalling...
Easy migration of VMs between hypervisors for emergencies or load balancing
QEMU/KVM virtual machine performance is very close to the performance on a real, physical host (Type 1 Hypervisor) - in contrast with Type 2 hypervisors (VirtualBox, VMWare Player...)

libvirt/virt-manager can be installed on a dedicated machine, or on any GNU/Linux desktop computer.

Installation

On Debian-based systems:

# base packages
sudo apt install virtinst dnsmasq-base libvirt-daemon-system qemu-kvm qemu-utils libguestfs-tools
# graphical tools (desktop machines only)
sudo apt install virt-manager virt-viewer

(Optional) add your normal/unprivileged user account to the libvirt group to allow it to manage virtual machines without using sudo/entering your password for common operations:

sudo usermod --appent --groups $USER libvirt,kvm,libvirt-qemu

Libvirt can also be installed and managed from xsrv, using the libvirt role.

VM creation

Manual

Run virt-manager from your applications menu and click New virtual machine

Select QEMU/KVM as the virtual machine type:

Select the installation media/ISO image for the operating system you want to install:

Set memory amount and virtual CPU number depending on your performance requirements:

Create a new virtual hard disk image for your VM depending on your storage requirements:

Set a unique name (such as a FQDN) for your VM, and attach it to the default NAT virtual network:

Click Finish and start the VM from virt-manager's main window.

Automated

You can also create a VM from the command-line using the virt-install command. The xsrv init-vm and xsrv init-vm-template commands automate running virt-install with the correct options.

Cloning VMs

See Debian/Installation/From a VM template, xsrv init-vm --help, and the following manpages:

Migrating VMs between hypervisors

# dump the VM xml definition
srvadmin@hv1:~$ virsh dumpxml my.virtual.machine > my.virtual.machine.xml
# copy the VM XML definition to the destination host
srvadmin@hv1:~$ rsync -avP my.virtual.machine.xml srvadmin@hv2.example.org:my.virtual.machine.xml
# copy the VM disks to the destination host (same directory)
srvadmin@hv1:~$ rsync -avP /var/lib/libvirt/images/my.virtual.machine.qcow2 srvadmin@hv2.example.org:/var/lib/libvirt/images/my.virtual.machine.qcow2
# ssh to the destination host
srvadmin@hv1:~$ ssh srvadmin@hv2.example.org
# create a VM from the XML definition
srvadmin@hv2:~$ virsh define my.virtual.machine.xml
# start the VM
srvadmin@hv2:~$ virsh start my.virtual.machine.xml

If your VMs are managed by the libvirt role, instead of dumping/transferring the XML definition and loading it manually, you should just copy the relevant libvirt_vms entry to the target hypervisor host_vars, and set its state to absent on the original hypervisor. Don't forget to migrate any libvirt_port_fowards related to it.

Alternatives

Proxmox VE, a dedicated hypervisor manager based on Debian/KVM