Adding a secondary qemu2 disk to a kvm using virsh

First create the image:

qemu-img create -f qcow2 /var/kvm/images/vm-secondary.qcow2 50GB

Then attach it to the virtual machine:

virsh attach-disk vm /var/kvm/images/vm-secondary.qcow2 vdb --persistent --subdriver qcow2

Enter VM and format disk, you don’t need to restart.