Hardware-backed FDE selected as default and no other option available

Michael Hudson-Doyle asked me to use a larger disk image for the installation so I switched from 20G to 40G and then was allowed to choose different installation options. For the record this is how I setup the virtual machine:

 $ virt-install --os-variant ubuntu22.04 --name ubuntu-canary-install --memory 4096 --disk /srv/vms/mantic-install.img --cdrom /misc/isos/ubuntu/mantic-desktop-canary-amd64.iso --machine q35 --features smm.state=on --boot loader=/usr/share/OVMF/OVMF_CODE.secboot.fd,loader.readonly=yes,loader.type=pflash,nvram.template=/usr/share/OVMF/OVMF_VARS.ms.fd,loader_secure=yes --hostdev 06:00.0,address.type=pci --check path_in_use=off --tpm backend.type=emulator,backend.version=2.0,model=tpm-tis

The '--hostdev' argument is for a Broadcom wireless card.

I tested this today with the image from https://cdimage.ubuntu.com/ubuntu/daily-canary/20230822.1/ and this bug seems to have been fixed. FDE install is not ticked by default

I spoke with Dan Bungert about this and he indicated that it is still possible to encounter this scenario but 20G might not be the magic number i.e. it could happen with a different disk size so I think we should still keep this bug report open.

We discussed it a bit further and my understanding is that the minimum disk size for an FDE install is smaller than the size necessary for a classic install. Subsequently, having FDE selected as the default and only option is actually correct. Additionally, the size necessary for any install option is variable depending on the amount of RAM the system has as that is used to allocate swap space. Regardless, I think we should add release note entry regarding different install options being available dependent upon the size of the disk upon which we are installing.

bug #2033244 is resolved in canary image 20230830 and later. However, I'm not sure this has addressed the case of selecting FDE when no other options are available. So that should be validated still.

Tested with virt-install --disk ./mantic-install.img,size=10:

"Not enough disk space to install Ubuntu

Required: 14.03GB
Available: 10.74GB"

--disk ./mantic-install.img,size=13:

"Not enough disk space to install Ubuntu

Required: 14.03GB
Available: 13.96GB"

--disk ./mantic-install.img,size=13: both the classic option and the TPM option are available. The classic option is selected by default.

It is impossible to say from the UX whether this is fixed because of improved logic in u-d-i, or because the calculated size requirements for the TPM install option have increased to the point that this situation no longer occurs.

there were two problems here
1) defaulting to the core boot capability flag -> fixed
2) the sizing recommendations -> the classic sizing recommendation is a bit high, we're adjusting that downward. The core boot one is low, we're adjusting that upward.

@dbungert

Also 3) during FDE call this morning "both types should be treated equivalent", meaning for both installation types consider the highest disk space requirement for both types. This is for the end user perception - either install type should always require the same disk space (irrespective of the internal, true, calculations for each of them)

https://github.com/canonical/subiquity/pull/1781 is expected to resolve items #2 and #3 above. When this is merged I don't expect we will need to release note it.

Changed size recommendations merged for subiquity. Another round of updates will be needed before this appears in the u-d-i snap.