Super generic preseed file for Ubuntu 20.04

user-data

#cloud-config
autoinstall:
  version: 1
  refresh-installer:
    update: yes
  apt:
    geoip: true
    preserve_sources_list: false
    primary:
    - arches: [amd64, i386]
      uri: http://us.archive.ubuntu.com/ubuntu
    - arches: [default]
      uri: http://ports.ubuntu.com/ubuntu-ports
  network:
    version: 2
    ethernets:
      eth0:
        dhcp4: yes
  identity:
    hostname: ubuntu-fresh
    realname: Edwin Jarvis
    username: jarvis
    password: <crypted password>
  keyboard:
    layout: us
    toggle: null
    variant: ''
  locale: en_US
  ssh:
    allow-pw: false
    authorized-keys:
      - ssh-rsa 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 misterk71@gmail.com
    install-server: true
  storage:
    layout:
      name: lvm
      match:
        ssd: yes
        size: largest
  user-data:
    disable_root: true
  late-commands:
    - echo 'jarvis ALL=(ALL) NOPASSWD:ALL' > /target/etc/sudoers.d/jarvis
    - sed -ie 's/GRUB_CMDLINE_LINUX=.*/GRUB_CMDLINE_LINUX="net.ifnames=0 ipv6.disable=1 biosdevname=0"/' /target/etc/default/grub
    - curtin in-target --target=/target -- update-grub2
    - curtin in-target --target=/target -- apt update
    - curtin in-target --target=/target -- apt upgrade -y