Libvirt pools contain volumes. There is a default pool, called “Default” which is defined during the KVM installation. You can create volumes in the Default pool, or you can define another pool and place the newly installed volume in the new pool. When you create a new volume, you can either do it through Virtual Machine Manager (which is piictured below) or you can do it via CLI using libvirt. Here is the BASH script for the libvirt volume:
qemu-img create -f qcow2 /var/lib/libvirt/images/qemu-img/ubuntu-qemu.qcow2 20G
This will create the volume, but not the pool. Once the volume is created you can create the pool via VMM or you do it via command line, and place the volume in that newly build pool. It is probably imperative that at this point, if not before, you get yourself familiar with this page:
Here are pictures of a Default pool,
and another user-defined pool, named “qcow2”.
As you can see, if both screenshots the file pathname is shown, the Default uses /var/lib/libvirt/images and for the qcow2 Pool, the pathname is /var/lib/libvirt/images/qemu-img.