Virtclone

Virt-clone is a command-line utility in the libvirt virtualization toolkit used to clone existing virtual machines managed by libvirt on Linux hosts running QEMU/KVM. It automates the duplication of a VM's configuration and its disk image to create a new, independently managed guest, often sharing storage only through backing files where supported.

How it works: Virt-clone reads the XML description of a source virtual machine, then creates a new domain definition with a distinct name and a new UUID. It duplicates the disk image(s) for the new VM, either by performing a full copy or by creating a linked clone if the storage format (such as qcow2) and filesystem allow it. The tool can generate new MAC addresses for network interfaces and adjusts other identity details to prevent conflicts. Depending on options, it may also modify the VM’s hostname or initial networking configuration.

Usage: Typical usage is: virt-clone --original sourcevm --name newvm --file /var/lib/libvirt/images/newvm.img. The --file option is optional; without it, virt-clone chooses a default path. The command may require the source VM to be stopped to ensure a clean clone, though some storage backends support online cloning via snapshots. After cloning, you can start the new VM and customize its network and OS settings as needed.

Limitations and considerations: Cloning consumes additional storage and may require significant time for large disks. If a linked clone is used, the clone relies on the base image for data, which can affect backups and updates. You must ensure unique MAC addresses and often adjust the guest OS network configuration, hostname, and licensing as appropriate. The exact behavior can vary across libvirt versions and storage backends.

See also: libvirt, QEMU, virt-manager, virt-builder, qcow2.