download the root disk image itself with this. There were a bunch of missing bits to make this nice though:

First of all, for raw disk images we need to attach them to a loopback block device, to make them mountable. Easy-peasy, systemd-dissect --attach already delivers that.

Then, for tar disk images we need to bind mount the downloaded and unpacked image to /sysroot/ (which is where the rootfs goes before we transition into it).

Net result of this: I can now point my UEFI to a single URL where it will load the UKI from. A few seconds later the initrd will pick up the rootfs from the same source, and boot it up. Magic!

Why all this though?

It's mostly to tighten my test loop a bit, for physical devices. So here's what this entails:

1. You build your image with mkosi one your development machine, and ask it to serve your image as HTTP. In other words: `mkosi -f serve`.

2. You boot into the target machine once, and register an EFI variable that enables HTTP boot from your development machine. Simply do `kernel-bootcfg --add-uri=http://192.168.47.11:8081/image.efi --title=testloop --boot-order=0`, using @kraxel's wonderful tool.

3. You simply reboot that target machine. It will now fetch the UKI kernel, which then fetches the root disk image. And everytime you reboot this happens again. The target's machine#s local disks are unnaffected.

4. …

5. Profit!!