New project: memdisk_uefi

[russor]

Hey all, I got inspired and built something like Syslinux's MEMDISK, but for UEFI:

https://github.com/russor/memdisk_uefi

I've only tested on VMWare amd64, but hopefully it works elsewhere too. It uses iPXE's UEFI download protocol to fetch a disk image, mounts it via UEFI Ram Disk Protocol, exposes the image as a NVDIMM, and then boots from the mounted image.

Like with memdisk, early init of the OS will likely use system facilities and be able to access the ramdisk with no problem, but once the OS kernel exit's UEFI boot services, it needs to find and use the image. Thankfully, NVDIMM has been around for a while, so there's some support already. Linux has had a driver since 2015, and FreeBSD has had a driver since 2018; I know the FreeBSD installer needs manual help to load the nvdimm driver, but the one Linux ISO I had on hand (ubuntu-24.04.1-live-server) did automatically load the driver; I don't know if this is common or not.

This might help setup UEFI netbooting for more distributions, without having to deconstruct installer images as is often the case.