sorry ,I misunderstand your meaning.
I try with 'virsh -c qemu+ssh://root@192.168.7.126/system' as follows:

root@Optiplex-780:/var/log/apache2# virsh -c qemu+ssh://192.168.7.126/system
root@192.168.7.126's password:
error：server closed connection:
error：连接到管理程序失败(failed to connect to the monitor?)
root@Optiplex-780:/var/log/apache2#

best regards,
qinguan

2011/5/5 Daniel P. Berrange <berrange@redhat.com>
On Thu, May 05, 2011 at 06:46:32PM +0800, guan qin wrote:
> yeh,it's working !
> I can see that the VM already running and never kill itself now.
> I appreciate your help very much.
>
> but I meet another problem after I upgrade the libvirt version from 0.8.3 to
> 0.9.0.
> I find that if I use "virt-viewer -c
> qemu+ssh://192.168.7.126/systemvt_d_ubuntu",
> the machine shows a message that "Unable to connect to libvirt with URL
> qemu+ssh://192.168.7.126/system ".

This is ssh'ing as an unprivileged user, and so it likely doesn't have
permission for the socket. You can try  'qemu+ssh://root@192.168.7.126/system'
instead

Also see these pages

 http://wiki.libvirt.org/page/Main_Page#SSH

Daniel
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