I installed the Cumulus VX 3.7.2 appliance in GNS3 2.1.11, but the instructions for configuring don't work. I am following https://docs.cumulusnetworks.com/display/VX/Getting+Started. Is this the right guide? I then followed the KVM/Qemu section at https://docs.cumulusnetworks.com/display/VX/Libvirt+and+KVM+-+QEMU. It fails trying to install libvirt because the apt-add-repository command cannot be found. Any help is greatly appreciated.