Question about bootup

[Nathan Whitehorn]

[Not replying to the top bits, since the others covered that correctly]

On 03/06/12 00:24, Rob Ballantyne wrote:
> Hi All,
>
>    I've been poking around trying to understand the boot up process of
> a ppc64 G5 machine.
>
>    I was slightly surprised to still find an Apple Partition map disk.
> I would have thought it was an ordinary fdisk (PC) partition setup.
>
>    Let me see if I have it right:
>
> 1 - OpenFirmware (OFW) load Apple_Bootstrap/boot1.elf
> 2 - boot1.elf runs to gain enough to understand UFS filesystems and
> loads FreeBSD UFS partition /boot/loader
> 3 - loader loads /boot/kernel/kernel
>
> ... and we're off to the races.
>
>    This strikes me as fairly simplistic so I'm sure there are more
> details.  I'm curious about /boot/*.4th OpenFirmware forth code, for
> example.  Is it involved in a substantial way?
>
>    The other thing I'm curious about is the Apple_Bootstrap partition.
> How is it written?  I've discovered parteditor within the bsdinstall
> installer.  I suspect that does it but it doesn't appear to let one
> write their own bootloader code  image.
>

It is written by the installer, in the partition editor. You can see 
what it does by looking at 
/usr/src/usr.sbin/bsdinstall/partedit/partedit_powerpc.c. It just dd's a 
preformatted HFS partition from /boot/boot1.hfs onto the bootstrap 
partition.
-Nathan