[libvirt-users] authentication failed, but why?

I set the me into the group libvirt and write the config for libvirtd: ================================================== listen_tls = 0 listen_tcp = 0 auth_tcp = "none" mdns_adv = 0 unix_sock_group = "libvirt" unix_sock_ro_perms = "0770" unix_sock_rw_perms = "0770" unix_sock_dir = "/var/run/libvirt" log_filters = "1:libvirt 1:util 1:qemu" log_output = "1:file:/var/log/libvirt/libvirtd.log" max_clients = 500 min_workers = 10 max_workers = 50 max_requests = 50 max_client_requests = 8 =========================================== but I can't login the libvirt: [xxxxxx@u70 ~]$ virsh error : authentication failed: Authorization requires authentication but no agent is available. who can tell me why? thanks a lot. :)