Net-booting an EFI image on an aarch64 server with iPXE script

[travislazar]

I think I'm coming to a better understanding about the bootloading process, but need some clarification/validation.

If I understand this correctly, iPXE is a bootloader in a similar vein as Grub. So with iPXE, if you can load the right kernel and initrd images, you can boot/pass control straight to those images. However, in my case, where I use sanboot to load an ISO, I'm loading this image into memory, mounting it as a "CDRom Drive", and booting to it through grub. So in the sanboot case, grub takes over as the bootloader instead of iPXE.

Is this a correct understanding?

If I wanted to continue with the grub method (thought experiment here), could I modify the ISO file's grub.cfg to be something like:

Code:

set timeout=3
set default=0

menu ......
    /linux preseed/url=path/to/preseed auto=true --- quiet
...

And then repackage the ISO? That, in theory, should tell grub to auto run the first menu item after 3 seconds, and the first menu item would have linux imgargs built into the grub.cfg file? Seems a little hacky, but functional, and within the bounds of what grub is intended to do.

So then where do EFI scripts come in to play? I'm having issues imgfetching the linux image provided by Ubuntu in the arm64 netboot folder. I get error 2e008081 every time I try to load an arm64 linux image from Ubuntu's build repo. My gut is telling me that the image is not EFI compatible (is there a way to test this?). There is however a bootnetaa64.efi file, which seems applicable in my situation.

So back to a question about how iPXE works here - if I try to execute an EFI file through imgload/initrd, does it drop the system into the EFI shell and execute those scripts? Is EFI then responsible for loading and passing control to the right initrd image? Does iPXE ever gain control back?

Do I also need to imgfetch -n any other files from the Ubuntu repo? Like:

Code:

imgfetch -n linux http://..linux,
imgfetch -n initrd.gz http://..initrd.gz
imgload -n bootnetaa64.efi http://..bootnetaa64.efi

Would that work? My current testing is imgloading the bootnetaa64.efi file, but when I do a boot command I get dropped into the EFI shell with no filesystems mounted and no error messages at all.