[Gllug] Installing grub from a recovery CD

[John Winters]

On Thu, 2005-02-24 at 17:19 +0000, Ben Fitzgerald wrote:
> On Thu, Feb 24, 2005 at 04:47:05PM +0000, John Winters wrote:
> > On Thu, 2005-02-24 at 08:32 +0000, Tethys wrote:
> > > John Winters writes:
> > > 
> <snip>
> > 
> > Perhaps they do it because you've got to have *something* in the MBR,
> > and if Linux is the only OS on the box you won't have the MS-DOS boot
> > loader there?
> 
> Is this correct? I thought that if you mark a partition as bootable
> in your drive partition table (which IIRC is in the first 512 bytes)
> then your bios will try to boot the first sector in that?

My understanding is that all your BIOS will do is load and boot
whatever's in the MBR.  This historically would be the MS-DOS boot
loader, which is the thing which then selects and boots the first
partition marked as active.  If you're using something more
sophisticated in the MBR (e.g. LILO or Grub) then the "active" partition
is irrelevant.  (Although I believe some versions of Windows can get
upset if they think they're running from a non-active partition.)

> 
> > > >This is easy using lilo - just mount the partitions and do a "lilo -r",
> > > >and I presume it must be possible with grub too but I can't find any
> > > >clues in the grub documentation.  Can anyone give me a pointer please?
> > > 
> > > 	grub-install /dev/hda
> > 
> > According to the man page for grub-install this does *not* do what I
> > want.  All I need to do is reinstall the element of grub which lives in
> > the MBR.
> 
> I don't think this is correct as you will need to change your grub
> config file to include an entry for your windows partition.

That's not a problem, and can be done at any stage.  The first
requirement is just to get grub running as part of the boot sequence.

> 
> > This is what puts me off grub - the documentation is *still* very poor,
> > and in particular it uses terms like "root directory" to mean something
> > different from what it usually means, *without first saying what the
> > re-definition is*.
> 
> have you tried the info pages for grub? they are much better.

Yes.  They still didn't contain the necessary information.

All up and running now, thanks to Phil's instructions and some
hand-holding by Ivan.  Thanks all.

John

-- 
John Winters <john at sinodun.org.uk>

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