Ubuntu 20.04 default autoinstall storage confusion

[Drew Weaver]

Normally when deploying an OS using an autoinstall method if you don't supply any instructions on how to handle the storage it either stops and prompts you for storage configuration OR it will just follow the default in the regular installer.

In Ubuntu 20.04 it appears that if you don't supply anything in the autoinstall YAML file for storage that it creates a 100% size VG and then a 1% LV and puts the / filesystem in the 1% LV.

This is the user-data file that I used to install:

#cloud-config
autoinstall:
  version: 1
  ssh:
    allow-pw: true
    install-server: true
  identity:
    hostname: ubuntu-server
    password: "removed"
    username: ubuntu

The resulting /var/log/installer/autoinstall-user-data file is this:

storage:
    config:
    - {ptable: gpt, serial: 364cd98f0bf735f00263bfbff03a8d528, wwn: '0x64cd98f0bf735f00263bfbff03a8d528',
      path: /dev/sda, wipe: superblock, preserve: false, name: '', grub_device: true,
      type: disk, id: disk-sda}
    - {device: disk-sda, size: 1048576, flag: bios_grub, number: 1, preserve: false,
      type: partition, id: partition-0}
    - {device: disk-sda, size: 1073741824, wipe: superblock, flag: '', number: 2,
      preserve: false, type: partition, id: partition-1}
    - {fstype: ext4, volume: partition-1, preserve: false, type: format, id: format-0}
    - {device: disk-sda, size: 478483054592, wipe: superblock, flag: '', number: 3,
      preserve: false, type: partition, id: partition-2}
    - name: ubuntu-vg
      devices: [partition-2]
      preserve: false
      type: lvm_volgroup
      id: lvm_volgroup-0
    - {name: ubuntu-lv, volgroup: lvm_volgroup-0, size: 4294967296B, preserve: false,
      type: lvm_partition, id: lvm_partition-0}
    - {fstype: ext4, volume: lvm_partition-0, preserve: false, type: format, id: format-1}
    - {device: format-1, path: /, type: mount, id: mount-1}
    - {device: format-0, path: /boot, type: mount, id: mount-0}

And there really isn't any explanation for why it's choosing to do what it is choosing to do.

My Ubuntu 16 kickstart file (which does exactly what I want) looks like this for the storage configuration:

zerombr yes
clearpart --all --initlabel
preseed partman-auto/choose_recipe select atomic
preseed partman/choose_partition string finish
preseed partman/confirm boolean true
preseed partman-lvm/device_remove_lvm boolean true

Does anyone know why it's making the LV and the resulting filesystem this size? 4294967296B How can I tell it to just use the entire SDA?

The docs are really confusing.

Thanks,
-Drew

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