Text 1513, 69 rader
Skriven 2004-09-27 19:33:02 av Paul Rogers (1:105/360.0)
     Kommentar till en text av Pascal Schmidt
Ärende: Getting grubby
======================
 PS> command line. ;) syslinux knows FAT and isolinux knows
 PS> ISO9660.

And IIRC it has a kernel on the floppy.

 PS> correct signature (the last two bytes need to be 0x55 0xAA),

It makes me laugh when they call them the "magic bytes".  Back
in the days of FM/MFM 8" diskettes we knew that as the initial
format of blank disks.  (Note the alternating bit pattern.)

 PS> The reason why installing a bootloader on /dev/hdc and then running the
 PS> same  disk as /dev/hda doesn't work out (unless the bootloader
 PS> installer program knows how to prepare the bootloader for
 PS> this situation) is that the bootstrap code has to use BIOS
 PS> hard disk adressing to load the second stage boot code. The
 PS> BIOS numbering changes when you switch the disk around, and
 PS> so the bootstrap code (one sector is only 512 bytes long,
 PS> so the bootstrap code has to be short and as a consequence,
 PS> pretty dumb) ends up looking in the wrong place.

Not good enough.  Why does the first stage need to worry about
which drive/partition it's on?  All partitions have room for
boot code, although they're traditionally unused (though grub
can chain-load them).  I expected grub to jump to the (second?)
sector of the same disk to find the second stage.  Just presume
you're booting from whatever disk/partition you're in.

 PS> filesystem. Personally, I don't like the fact that grub
 PS> invented yet another way to name hard disks and partitions -
 PS> - that hd(X,Y) stuff.

Well, it isn't Linux based, and hardware usually counts from
zero.

 PS>> Why did you have an incorrect fstab to start with? I'm
 PR> Because I did change the layout and edited /etc/fstab when I
 PR> THOUGHT I was editing /mnt/hd/etc/fstab.
 PS> Ah. May I suggest doing "chroot /mnt/hd" before, next time? ;)

So I forgot to "cd /mnt/hd" but I'd remember to chroot?  ;-)

 PR> Booting from a grub floppy doesn't require the kernel to be on it!
 PS> So what do you do when you screwed the kernel image on the
 PS> hard disk? Or like in your situation, what to do when you
 PS> can't really boot the system on hard disk because its
 PS> /etc/fstab is far removed from reality? For such
 PS> situations, nothing can beat a CD-ROM rescue system, which
 PS> doesn't rely on *anything* on the hard disk working.

I was thinking of a comparison of a grub boot floppy and a lilo
boot floppy.  As for syslinux, see above.

 PS> Shameless plug: http://www.minimalinux.org/ttylinux/ -- I
 PS> do provide a bootable ISO image. 3MB download (but the
 PS> kernel used does not support SCSI, so YMMV).

It's good, eh?  I suppose that makes it worth a link on my
Nerd Zone page.

Paul Rogers, paulgrogers@yahoo.com                       -o)
http://www.angelfire.com/or/paulrogers                   /\\
Rogers' Second Law: Everything you do communicates.     _\_V

... Lose not thy airspeed, lest the ground arise & smite thee
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