Re: [RFC] x86 ELF bootable kernels/Linux booting Linux/LinuxBIOS

Rob Landley
2002-02-03T23:46:21Z

On Sunday 03 February 2002 06:01 pm, H. Peter Anvin wrote:
> Rob Landley wrote:
> > You can pivot_root after the bios hands control over to the kernel, sure.
> > But if the bios can actually boot from arbitrary blocks on the CD before
> > the kernel takes over, this is news to me. And for the kernel to read
> > from the CD, it needs its drivers already loaded for it, so they have to
> > be in that 2.88 megs somewhere. (Statically linked, ramdisk, etc.)
>
> No, the boot specification allows direct access to the CD. See the El
> Torito specification, specifically the parts that talk about "no
> emulation" mode.

Thanks. I'd missed that.

> > Now I'm not so familiar with that etherboot stuff, intel's whatsis
> > specification (PXE?) for sucking a bootable image through the network.
> > All I've ever seen that boot is a floppy image, but I don't know if
> > that's a limitation in the spec or just the way people are using it...
>
> That's just the way *some* people are using it. Look at PXELINUX for
> something that doesn't. PXELINUX can use the UDP API provided by the
> PXE specification to download arbitrary files, specified at runtime, via
> TFTP.

That one I suspected. (I used the TFTP setup on solaris and power PC years
ago, just didn't know if x86 bioses had caught up. Most of my BIOS
experience in the past few years has been with Dell machines, so my
expectations may have been unnecessarily lowered... :) On the other hand,
very few systems in the field seem to boot and install entirely through the
network unless they're meant to be diskless...

> -hpa

Rob