Booting an alternate kernel

[Roman Bogorodskiy]

  Justin Hibbits wrote:

> Hi Roman,
> 
> Not a direct answer to your question, but more addressing what your
> real problem might be.
> Are you booting powerpc or powerpc64?  Powerpc (32-bit) got updated to
> 64-bit time_t, which requires everything new.  Easiest way to update
> that is a fresh install (See UPDATING note 20170625).
> 
> - Justin

Thanks for the pointer, I'm booting powerpc indeed.

> On Mon, Jan 8, 2018 at 12:17 PM, Roman Bogorodskiy <novel at freebsd.org> wrote:
> > Hi,
> >
> > Recently I upgraded FreeBSD -CURRENT as of mid-2016 to a fresh one (Jan
> > 6-7 -CURRENT). Of course I didn't read UPDATING and missed 20171125
> > entry so it failed to find root. However, when I manually set root to
> > 'ufs:/dev/ada0s3', it failed to boot because init segfaulted (I did
> > installkernel but not installworld).
> >
> > I decided to boot kernel.old. There's a note here:
> >
> > https://www.freebsd.org/platforms/ppc.html#issues
> >
> > that tells how to boot a custom kernel, e.g. doing
> >
> > 0 > boot hd:loader hd:0
> >
> > It doesn't work for me.
> >
> > I figured out that I can proceed to normal boot from the OpenFirmware
> > shell using
> >
> > 0 > boot hd:\ppc\boot1.elf
> >
> > But I don't quite understand how to specify invalid partition?
> >
> > I tried things like "boot hd:\ppc\boot1.elf hd:4" but it appears to
> > treat "hd:4" as a loader.
> >
> > As far as I understand, boot1.elf source code is:
> >
> > https://github.com/freebsd/freebsd/blob/master/stand/powerpc/boot1.chrp/boot1.c
> >
> > From what I can see:
> >
> > https://github.com/freebsd/freebsd/blob/master/stand/powerpc/boot1.chrp/boot1.c#L414
> >
> > it only allows to define 'path' which is PATH_LOADER "/boot/loader" by
> > default; and bootpath is set from /chosen bootpath property.
> >
> > Would appreciate if somebody could help with the follow:
> >
> >  * How do I force invalid 'bootpath' so it drops into loader without
> >    loading kernel (or other ways to load kernel.old)?
> >  * Hints how to debug init segfault issue
> >
> > Thanks,
> >
> > Roman Bogorodskiy

Roman Bogorodskiy
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