The official Met asp loitable system only releases vmdk files, which can be opened directly with VMware, but how to use it in KVM? Very helpless, but fortunately there is a problem to solve, do a format conversion
qemu-img convert -f vmdk -O qcow2 Metasploitable.vmdk Metasploitable.img
qemu-img info Metasploitable.img
vmware2libvirt -f Metasploitable.vmx > Metasploitable.xml
virsh -c qemu://system define Metasploitable.xml
sudo virt-manager
Haha, now you can open it with KVM.