Instalar QEMU/KVM no debian
#
apt install qemu-kvm qemu-system qemu-utils libvirt-clients libvirt-daemon-system virtinst virt-manager bridge-utils libvirt-clients-qemu libvirt-login-shell ssh-askpass 
#

#/etc/qemu/bridge.conf
#allow br0
#
systemctl enable libvirtd
#
vi /etc/network/interfaces
...
##############################

auto lo
iface lo inet loopback

# DHCP IP address

auto eth0
iface eth0 inet manual
#
auto br0
iface br0 inet dhcp
      bridge_ports eth0 #sendo a interface que quer usar como mestre
      bridge_stp off
      bridge_fd 0
      bridge_maxwait 0

##############################

auto lo
iface lo inet loopback

# Static IP address

auto eth0 
iface eth0 inet manual
#
auto br0
iface br0 inet static
      address   192.168.1.227
      netmask   255.255.255.0
      network   192.168.1.0
      broadcast 192.168.1.255
      gateway   192.168.1.1
      bridge_ports eth0 #sendo a interface que quer usar como mestre
      bridge_stp off
      bridge_fd 0
      bridge_maxwait 0

##############################

Criar e Configurar a Bridge:
Edite o arquivo de configuração de rede para adicionar uma bridge. 
Abra o arquivo de configuração de rede (em modo root):

nano /etc/network/interfaces

Adicione a configuração da bridge:

auto br0
iface br0 inet dhcp
      bridge_ports eth0 #sendo a interface que quer usar como mestre
      bridge_stp off
      bridge_fd 0
      bridge_maxwait 0

Substitua eth0 pela interface de rede correta, que pode ser verificada com ip a.

Reiniciar o Serviço de Rede:
Após editar o arquivo, reinicie os serviços de rede para aplicar as mudanças:

#sudo systemctl restart networking

#qemu-system-x86_64 -hda /path/to/your/disk.img -m 2048 -net nic -net bridge,br=br0


#ssh root@192.68.10.252 -X
#virt-manager
video:
Configurar Debian como servidor de virtualizacion con QEMU/KVM

#
#printf -v macaddr "52:54:%02x:%02x:%02x:%02x" $(($RANDOM & 0xFF)) $(($RANDOM & 0xFF)) $(($RANDOM & 0xFF)) $(($RANDOM & 0xFF))
#echo $macaddr
#ex
#spice://192.168.1.157:5930