grub error 22. Bad partition table? [solved]

[John Summerfield]

On Friday 26 November 2004 04:23, John DeDourek wrote:
> Duncan Lithgow wrote:
> > I'd better mark this thread solved...
> >
> >> That suggests to me that it's probably safest to put grub in hda1 or
> >> so, and mark that partition bootable.
> >
> > That's the default isn't it? Paul said that MBR is in the first part of
> > hda1 - and because I'm also running windows it _has_ to be marked
> > bootable (or somewhere before 1024 has to)
> >
> > Thanks again for the help
> >
> > Duncan
>
> Just a clarification.  There is a boot block at the beginning of
> disk (BEFORE the first partition) and a boot block at the beginning
> of every partition.  "MBR" refers to the boot block at the beginning
> of the disk.

R==record. The first secor, 512 bytes.

The code I was inspecting fits into onse sector.

>
> Now, something that I'm less sure of.  If you put grub into the MBR
> (means code in the MBR and the 1.5 stage in the following sectors)
> then it can boot any partition, marked "bootable" or not.

True.

>
> If you install grub in some other partition (technically the boot
> block of that partition with stage 1.5 in the following sectors)
> then the code executed first will be whatever is installed in MBR.
> If that code is installed by windows, then I believe that it loads
> the code from the boot block of whichever partition is marked
> bootable.  That would have to be the partition with grub in the
> boot block if you want to bring up grub.

The code in the MBR finds the first "bootable" partition. This is the coe 
Windows installs to clobber Grub.

Back when I used to (sometimes) use Windows NT and (mostly) OS/2 Microsoft 
documented how to make "the other OS bootable." One went into Disk Mmngler 
and marked the other partition bootable.

Normally that other parition contained OS2/ Boot Manager.

>
> Now if you want that grub to chain load windows, I think (but am
> not sure) that you need to change which partition is bootable
> (using grub commands in  grub.conf) to mark the windows partition
> bootable before you chain to its boot loader.

There was no mucking around needed with Boot Manager. Whether I booted OS/2, 
NT or Linux with it, on the next reboot Boot Manager got started.

Installing Windows NT after OS/2 caused NT to boot in place of Boot Manager, 
but that was easily overcome as I've already mentioned.

> Perhaps someone more knowledgeable about grub could confirm or
> correct this latter comment.

-- 
Cheers
John