[TUHS] Pre-init initialization

[Warner Losh]

On Thu, Aug 8, 2019, 7:47 PM Grant Taylor via TUHS <tuhs at minnie.tuhs.org>
wrote:

> On 8/7/19 7:04 AM, Clem Cole wrote:
> > FWIW: V7 had /stand which was a funky UNIX-like standalone system that
> > some applications could be compiled.
>
> I've seen /stand on a few systems (I think SCO OpenServer and / or
> UnixWare) but never really knew what it was for.  I think I had naively
> assumed it was associated with the kernel and / or booting.
>
> Now I'm somewhat more curious what it was.  Was it a simplified version
> of the OS with minimal utilities with fewer dependencies so that the
> system could boot and load more features.
>

Yes. There was a library that implemented much of the unix API in a
simplified way that ran on bare metal.

I thought that Linux's initramfs / initrd had the usual suspect files /
> utilities copied from /.  So the idea that a utility in /stand would be
> different from the same utility in / seems strange to me.
>

They are because there was no kernel for them to run under. They were
similar, but if you go look at the sources, they are different.

> The problem was that it was a little different so you would end up
> > seeing #ifdef STAND in code for things like fsck, fsdb, even cat.
> > At Masscomp we ended up with three target environments for a couple of
> > the system maintenance utilities: the OS, /stand and the boot ROMS.
> > This was expensive/a PITA to maintain and keep straight, and in the
> > case of the boot ROM, space was a huge problem.
>
> Ya.  I can see how that would be a PITA to maintain.
>

FreeBSD, NetBSD and OpenBSD all implement some version of this. FreeBSD has
it in src/stand in honor of V7 stand. I did that when I integrate / rewrote
the GSoC project to bring Lua scripting to the boot loader. The other BSDs
have it split between sys/boot and lib/libs. FreeBSD uses it to implement
the rich boot loader which knows how to load off a lot of different file
systems and BIOS interfaces. Net/OpenBSD use it more modestly in their boot
loaders, but have a few standalone programs for things like bootstrapping
VAXen.

Warner

> The RAMFS idea was created to get rid of at least /stand and IIRC we
> > were able to drop a number of utilities out of the boot ROM.  I'm not
> > sure how far they took it.   I left for Stellar and it was always the
> > way Stellix booted.
>
> ACK
>
>
>
> --
> Grant. . . .
> unix || die
>
>
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