Setup KVM on Ubuntu

https://medium.com/@artem.v.vasilyev/use-ubuntu-cloud-image-with-kvm-1f28c19f82f8
https://discourse.ubuntu.com/t/building-multipass-images-with-packer/12361
https://docs.ansible.com/ansible/latest/modules/virt_module.html
https://cloudinit.readthedocs.io/en/latest/index.html

Load an Ubuntu 18.04 server

Install packages to support KVM and cloud-init

sudo apt-get install cloud-utils qemu-kvm libvirt-bin ubuntu-vm-builder bridge-utils qemu-utils genisoimage virtinst

Setup a Bridge Interface

Debian network interfaces

# /etc/network/interfaces
# https://wiki.debian.org/BridgeNetworkConnections
source /etc/network/interfaces.d/*

# The loopback network interface
auto lo br0
iface lo inet loopback

# Set up interfaces manually, avoiding conflicts with, e.g., network manager
iface enp7s0 inet manual

# Bridge setup
iface br0 inet static
  bridge_ports enp7s0
    address 192.168.1.50
    broadcast 192.168.1.255
    netmask 255.255.255.0
    gateway 192.168.1.1

Ubuntu netplan

# /etc/netplan/01-netcfg.yaml
network:
  version: 2
  renderer: networkd
  ethernets:
    enp7s0:
      dhcp4: no
      dhcp6: no
  bridges:
    br0:
      interfaces: [enp7s0]
      dhcp4: no
      addresses: [192.168.1.50/24]
      gateway4: 192.168.1.1
      nameservers:
        search: [home]
        addresses: [192.168.1.1, 8.8.8.8]

Get Hashicorp packer and build custom image

cd packer
wget https://releases.hashicorp.com/packer/1.6.6/packer_1.6.6_linux_amd64.zip
unzip packer_1.6.6_linux_amd64.zip
sudo ./packer build ubuntu_build.json

sudo mkdir -p /var/lib/libvirt/images/base

sudo mv output-qemu/packer-qemu /var/lib/libvirt/images/base/ubuntu-20.04-server-cloudimg-amd64-cusomized.qcow2

Build VMs

Modify the network-config file with the correct network information for your vminstance

cd cloud-init
rebuild_vms.sh