Example 1

This allows you to name the image file.

sudo virt-clone --original [ original_instance ] --name [ new_instance ] --auto-clone --file /var/lib/libvirt/images/[ new_instance ].qcow2

If you have multiple disks

virt-clone --original [ old_instance ] --name [ new_instance ] --file /var/lib/libvirt/images/[ new_disk0 ].img --file [ new_disk1]-1.img --connect=qemu:///system --force

Example 2

This will auto-generate an image name.

virt-clone --original [ old_instance_name ] --name [ new_instance_name ] --auto-clone

Caveats

The SSH keys on the cloned vm's will be identical to the keys on the original vm so you'll need to regenerate those:

sudo rm -f /etc/ssh/ssh_host_*
sudo dpkg-reconfigure openssh-server

Troubleshooting

You might have a problem with udev renaming eth0 to eth1, i.e., you get the following error:

udev renamed network interface eth0 to eth1

sudo vi /etc/udev/rules.d/70-persistent-net.rules

delete the eth0 line - rename all instances of eth1 to eth0 reboot.