Below is my start.xml:

<domain type='kvm' id='12'>
            <name>start-ubuntu</name>
            <memory>1048576</memory>
            <currentMemory>1048576</currentMemory>
            <vcpu>1</vcpu>
           <os>
              <type>hvm</type>
              <boot dev='hd'/>
              ......

I start the machine   virsh create start.xml

virsh list

Id    Name                           State
----------------------------------------------------
 20    start-ubuntu                   running

I set id=12,but it is actually 20,I don't know why.

Thanks.