Re: Oldworld OF boot questions
Ethan Benson wrote:
> On Sat, Jun 10, 2000 at 08:05:41PM -0700, Chris Baker wrote:
> >
> > Maybe I can stand to lose something else in there. I'm not insisting
> > that anyone support my ideosyncrasies; I just want to know how to hack
> > it together myself 8-)
>
> there may already be enough space, im not sure, have not checked
> lately.
>
> however deleting most of the files there will do you no good since
> most of them are hard links to /bin/busybox.
>
> what you need to do is this:
>
> gzip -dc root.bin > root.bin.nogz
> mount -t ext2 -o loop root.bin.nogz /floppy
> cp /sbin/nvsetenv /floppy/sbin/
> umount /floppy
> rm root.bin
> gzip root.bin.nogz
> mv root.bin.nogz.gz root.bin
> dd if=/dev/zero of=/dev/fd0 bs=512 count=2880
> dd if=root.bin of=/dev/fd0 bs=512
>
> > > it would probably be better to integrate nvsetenv into busybox to save
> > > the overhead of a fully linked executable. i think it does belong
> > > there, perhaps for woody where we will hopefully be able to map /dev
> > > nodes to OF devices.
> >
> > I trust you know what you're talking about, since I haven't faintest
> > idea what this means....
>
> ;-)
>
> busybox is a bunch of stripped down basic unix utilities, ls, chmod,
> chown grep etc etc all compiled into ONE executable program. this
> program changes its behaviour based on the name its called as, so what
> you do is create a hard link from busybox to ls and run ls you get ls
> behaviour, make another link chown, and run chown you get chown's
> behaviour, etc.
>
> so when you look around on the boot floppies you will find most of the
> utilities have a link count of 60 or so, that is because they are all
> hard links to busybox. hard links take no disk space at all (unlike
> symlinks).
>
> why would anyone do such a strange hack? heres why:
>
> [eb@socrates eb]$ echo 'main(){}' > nothing.c
> [eb@socrates eb]$ cat nothing.c
> main(){}
> [eb@socrates eb]$ gcc nothing.c -o nothing
> [eb@socrates eb]$ ls -l nothing
> -rwxr-x--- 1 eb eb 4706 Jun 10 19:27 nothing
> [eb@socrates eb]$ strip nothing
> [eb@socrates eb]$ ls -l nothing
> -rwxr-x--- 1 eb eb 2972 Jun 10 19:27 nothing
> [eb@socrates eb]$ ./nothing
> [eb@socrates eb]$
>
> even a program that does absolutly nothing, contains no real code at
> all, has nearly 3K of overhead when stripped.
>
> this is because the executable has other various information embedded,
> such as the archecture and the shared library linking information,
> even though nothing.c contains no real code it is still linked against
> libc (main()):
>
> [eb@socrates eb]$ ldd nothing
> libc.so.6 => /lib/libc.so.6 (0x0feea000)
> /lib/ld.so.1 => /lib/ld.so.1 (0x30000000)
> [eb@socrates eb]$
>
> what busybox does is eliminate all that redunancy by wrapping all the
> base utilities into ONE executable.
>
> you won't really need to do this probably, unless there is not enough
> space, but the boot floppies people would assuming they decide to add
> this. that is what they did for mktemp which i needed for
> ybin/mkofboot to work.
>
> as for mapping /dev nodes to OF devices, the problem is that even
> though we know your root partition is /dev/hda2 on /dev/hda we have NO
> IDEA what that translates to in OpenFirmware, and there is currently
> no way to find out from the kernel. this means there can be no
> automated way for quik (oldworld) or ybin (newworld) to set the
> boot-device for you. (though on newworld its usually not necessary
> since the defaults usually work fine)
>
> > > you mean a non-miboot floppy? i think you can do that by putting a
> >
> > Yes, that's what I meant, but alternatives are welcome. I don't
> > really know what miboot is. I suppose boot-hfs-image (or whatever
> > it's called) is a miboot floppy, right? I just did a google search on
> > miboot, which didn't really come up with much aside from benh's page.
> > Are there any docs for it lying around?
>
> not really, miboot is intended for boot floppies/CDs not so much for
> disk bootstrap (which users are interested in) due to the problems
> with macos. (it likes to ruin miboot partitions)
>
> what miboot is is a fake System file, that actually contains boot
> loader code. its designed to look and load like the MacOS System
> file, this way the MacROM will load it like it would load macos and
> end up loading a boot loader instead. moboot also requires the MacOS
> boot blocks to be installed on the disk (in the fisrt 1K block of the
> filesystem) for a miboot floppy to work your OF boot-device must be
> /AAPL,ROM the hardware Mac ROM.
>
> > > COFF format kernel on a floppy and doing a boot fd: or something. im
> > > not sure i don't have an oldworld mac to tinker with, and newworlds
> > > have an annoying lack of a floppy..
> >
> > Ah! This is starting to sound familiar. It needs to be in COFF
> > format. How would one make such a thing? Let me guess: it's a
> > propriatary Apple format which isn't supported except for some hacked
> > together binutils from four years ago that everyone would just as soon
> > forget ever existed. Am I close?
>
> of course not! COFF is a standard executable format used by some
> unices, including Digital UNIX. all that is required to get a COFF
> format kernel is:
Note that this is automatically done by make-kpkg. If you have a kernel-image package
installed, just copy /boot/vmlinux.coff-`uname -r` to the floppy.
Zeen,
-Adam P.
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