I installed libvirt and virt-manager, but virt-manager isn't working. Is there a good tutorial on using virsh. I got the following message when creating a virtual machine in virt-manager:Error launching manager: 'NoneType' object has no attribute 'get_default_storage_format'Traceback (most recent call last):  File /usr/share/virt-manager/virtManager/engine.py, line 889, in _do_show_create    self._get_create_dialog().show(src.topwin, uri)  File /usr/share/virt-manager/virtManager/create.py, line 170, in show    self.reset_state(uri)  File /usr/share/virt-manager/virtManager/create.py, line 393, in reset_state    self.addstorage.reset_state()  File /usr/share/virt-manager/virtManager/addstorage.py, line 196, in reset_state    fmt = self.conn.get_default_storage_format()AttributeError: 'NoneType' object has no attribute 'get_default_storage_format'
manage virtual machines with virsh
libvirtd