[libvirt] error: failed to connect to the hypervisor

Hello, I have reinstalled libvirt-bin on ubuntu 9.04. Then I got a error: ------------------------------------------------------------------------ root@forest:/usr/local/etc/logrotate.d# virsh -c qemu:///system list error: failed to connect to the hypervisor ----------------------------------------------------------------------- ps: I have installed kvm on ubuntu. Any ideas? Regards Zhentao