Add install verb

[cgwalters]

We should support something as straightforward as

$ bootc install quay.io/examplecorp/mycustomos:latest /dev/nvme0n1

This would:

• Partition the disk in an opinionated way
• Install the bootloader
• Install the content from the container image

Partitioning

Obviously...there's a lot of tooling here. We should consider supporting at least Ignition as well as systemd-repart for nontrivial disk image setups.

Bootloader

For now, let's require that the target OS is setup using bootupd.

container image install

All the rest of the stuff (i.e. 99%) comes from the container image itself; we just need to call out to e.g. https://github.com/coreos/coreos-assembler/blob/d039e883059c48f2310572955682b9d25f4b6d61/src/create_disk.sh#L350

(Of course the steps above are also done in the example cosa code - we could hardcode some defaults, or probably better make it configurable in the image)

One idea here is to do a multi-stage fetch; we pull the container via e.g. podman (or actually instead, assume the UX is podman run --privileged quay.io/examplecorp/mycustomos:latest bootc install /dev/vda ? Then we can use something more like the deploy-from-self logic)

install --replace-booted-block-device

We could also support bootc install --replace-booted-block-device quay.io/examplecorp/mycustomos:latest which would implement this flow - basically, we:

• Move the running code into RAM (systemd switch root? Or just replace pid1 entirely)
• wipefs the booted block device
• Run the same install logic over that block device

install --switch-root

It'd make sense to support systemctl switch-root to the new target rootfs, but without using the new kernel. (But, we should be really clear when we're in a kernel != root situation)

[cgwalters]

I want to xref here https://bugzilla.redhat.com/show_bug.cgi?id=2125655