ubuntu kvm

Ubuntu server uses networkd for network rendering and Ubuntu desktop uses NetworkManager.

While you can find many places on the Internet explaining how to do a network bridge using NetworkManager, I’ve never seen it work.

You can switch your entire desktop workstation to networkd but you will lose the adantages of NetworkManager (WiFi, GUI support, …).

But you may have missed that both networkd and NetworkManager can be used together.

Network bridge on the server (/etc/netplan/01-config.yaml)

network:
  version: 2
  renderer: networkd
  ethernets:
    enp3s0:
      dhcp4: false
  bridges:
    br0:
      macaddress: XX:XX:XX:XX:XX:XX
      dhcp4: false
      interfaces:
        - enp3s0
      addresses:
        - XXX.YYY.ZZZ.10/16
      routes:
        - to: default
          via: XXX.YYY.ZZZ.1
      nameservers:
        search:
          - "lan"
        addresses: [XXX.YYY.ZZZ.1]

Network bridge on the desktop (/etc/netplan/01-config.yaml)

network:
  version: 2
  ethernets:
    eno1:
      renderer: networkd
      dhcp4: false
  bridges:
    br0:
      renderer: networkd
      macaddress: YY:YY:YY:YY:YY:YY
      dhcp4: false
      addresses: [ "XXX.YYY.ZZZ.20/24" ]
      nameservers:
        addresses: [XXX.YYY.ZZZ.1]
        search: [lan]
      routes:
        - to: default
          via: XXX.YYY.ZZZ.1
      interfaces:
        - eno1
      parameters:
        forward-delay: 0
        stp: false

You may need to reboot to force NetworkManager to ignore br0 and eno1.

Install libvirt on all machines

sudo apt-get install libvirt-daemon-system libvirt-clients
sudo usermod -aG kvm,libvirt $USER
sudo -i -u $user # or logout+login to enable groups

# remove the default (NAT network)
virsh net-undefine default
virsh net-define /dev/stdin <<EOF
<network>
  <name>host-br0</name>
  <bridge name='br0'/>
  <forward mode="bridge"/>
</network>
EOF

virsh net-autostart host-br0
virsh net-start host-br0

# define a boot pool
sudo mkdir -p /var/lib/libvirt/boot
sudo wget -P /var/lib/libvirt/boot https://cdimage.ubuntu.com/ubuntu-mini-iso/noble/daily-live/current/noble-mini-iso-amd64.iso
sudo chown libvirt-qemu:kvm /var/lib/libvirt/boot -R

virsh pool-define /dev/stdin <<EOF
<pool type='dir'>
  <name>boot</name>
  <target>
    <path>/var/lib/libvirt/boot</path>
  </target>
</pool>
EOF

virsh pool-autostart boot
virsh pool-start boot

On the desktop:

sudo apt-get install virt-manager

virt-manager will automatically connect to the local libvirt, but can be used to connect to a remote libvirt over ssh: `File -> Add Connection.. -> Connect

~~~

Question, remark, bug? Don't hesitate to contact me or report a bug.