vms over ubuntu

1. ubuntu需要修改emulator

   <emulator>/usr/bin/qemu-system-x86_64</emulator>

2. 需要cdrom引导安装系统

   <disk type='file' device='disk'>
       <driver name='qemu' type='raw' cache='none' io='native'/>
       <source file='/srv/vm/img/openEuler.raw'/>
       <target dev='vda' bus='virtio'/>
       <boot order='1'/>
   </disk>
   <disk type='file' device='cdrom'>
       <driver name='qemu' type='raw' cache='none' io='native'/>
       <source file='/srv/vm/img/openEuler-24.03-LTS-SP2-x86_64-dvd.iso'/>
       <target dev='sdb' bus='scsi'/>
       <readonly/>
       <boot order='2'/>
   </disk>