I set virt-manager in qemu:///system space and tried to add new VM but it didn't proceed. I figured out its duo to serial numbers is in cryptic form. # cat /sys/devices/virtual/dmi/id/product_serial ÿÿÿÿÿÿÿ #virt-manager --debug Traceback (most recent call last):   File "/usr/share/virt-manager/virtManager/libvirtobject.py", line 225, in _reparse_xml     self._xmlobj = self._build_xmlobj(self._get_raw_xml())   File "/usr/share/virt-manager/virtManager/libvirtobject.py", line 228, in _build_xmlobj     return self._parseclass(self.conn.get_backend(), parsexml=xml)   File "/usr/share/virt-manager/virtManager/nodedev.py", line 27, in _parse_convert     return NodeDevice.parse(conn, parsexml)   File "/usr/share/virt-manager/virtinst/nodedev.py", line 95, in parse     tmpdev = NodeDevice(conn, parsexml=xml, allow_node_instantiate=True)   File "/usr/share/virt-manager/virtinst/nodedev.py", line 106, in __init__     XMLBuilder.__init__(self, *args, **kwargs)   File "/usr/share/virt-manager/virtinst/xmlbuilder.py", line 777, in __init__     parent_xpath, relative_object_xpath)   File "/usr/share/virt-manager/virtinst/xmlbuilder.py", line 679, in __init__     self._parse(parsexml, parsexmlnode)   File "/usr/share/virt-manager/virtinst/xmlbuilder.py", line 692, in _parse     doc = libxml2.parseDoc(xml)   File "/usr/lib/python2.7/site-packages/libxml2.py", line 1327, in parseDoc     if ret is None:raise parserError('xmlParseDoc() failed') libxml2.parserError: xmlParseDoc() failed [Sun, 12 Apr 2015 06:06:16 virt-manager 4241] DEBUG (create:165) Showing new vm wizard [Sun, 12 Apr 2015 06:06:16 virt-manager 4241] DEBUG (create:892) Guest type set to os_type=hvm, arch=x86_64, dom_type=kvm [Sun, 12 Apr 2015 06:06:16 virt-manager 4241] DEBUG (xmlbuilder:694) Error parsing xml= <device>   <name>computer</name>   <capability type='system'>     <product>Vostro</product>     <hardware>       <vendor>Dell Inc.</vendor>       <version>A10</version>       <serial>ÿÿÿÿÿÿÿ</serial>       <uuid>REMOVED</uuid>     </hardware>     <firmware>       <vendor>Dell Inc.</vendor>       <version>A10</version>       <release_date>05/18/2013</release_date>     </firmware>   </capability> </device> [Sun, 12 Apr 2015 06:06:16 virt-manager 4241] ERROR (create:346) Error setting create wizard conn state. Traceback (most recent call last):   File "/usr/share/virt-manager/virtManager/create.py", line 344, in reset_state     self.set_conn(activeconn, force_validate=True)   File "/usr/share/virt-manager/virtManager/create.py", line 225, in set_conn     self.set_conn_state()   File "/usr/share/virt-manager/virtManager/create.py", line 626, in set_conn_state     self.netlist.reset_state()   File "/usr/share/virt-manager/virtManager/netlist.py", line 405, in reset_state     self._populate_network_list()   File "/usr/share/virt-manager/virtManager/netlist.py", line 253, in _populate_network_list     vnet_bridges)   File "/usr/share/virt-manager/virtManager/netlist.py", line 185, in _find_physical_devices     for nodedev in self.conn.get_nodedevs("net"):   File "/usr/share/virt-manager/virtManager/connection.py", line 648, in get_nodedevs     xmlobj = dev.get_xmlobj()   File "/usr/share/virt-manager/virtManager/libvirtobject.py", line 160, in get_xmlobj     self._reparse_xml()   File "/usr/share/virt-manager/virtManager/libvirtobject.py", line 225, in _reparse_xml     self._xmlobj = self._build_xmlobj(self._get_raw_xml())   File "/usr/share/virt-manager/virtManager/libvirtobject.py", line 228, in _build_xmlobj     return self._parseclass(self.conn.get_backend(), parsexml=xml)   File "/usr/share/virt-manager/virtManager/nodedev.py", line 27, in _parse_convert     return NodeDevice.parse(conn, parsexml)   File "/usr/share/virt-manager/virtinst/nodedev.py", line 95, in parse     tmpdev = NodeDevice(conn, parsexml=xml, allow_node_instantiate=True)   File "/usr/share/virt-manager/virtinst/nodedev.py", line 106, in __init__     XMLBuilder.__init__(self, *args, **kwargs)   File "/usr/share/virt-manager/virtinst/xmlbuilder.py", line 777, in __init__     parent_xpath, relative_object_xpath)   File "/usr/share/virt-manager/virtinst/xmlbuilder.py", line 679, in __init__     self._parse(parsexml, parsexmlnode)   File "/usr/share/virt-manager/virtinst/xmlbuilder.py", line 692, in _parse     doc = libxml2.parseDoc(xml)   File "/usr/lib/python2.7/site-packages/libxml2.py", line 1327, in parseDoc     if ret is None:raise parserError('xmlParseDoc() failed') parserError: xmlParseDoc() failed Regards Roz