[H-GEN] Cleaning up the MBR on a /dev/hda

[Jason Parker-Burlingham]

On Tue, Nov 15, 2005 at 03:42:43PM +1000, Ewan Edwards wrote:
> On Tuesday 15 November 2005 12:17, Jason Parker-Burlingham wrote:
> > I believe that standard Linux fdisk has -lu options which would be
> > similarly useful.  It would probably be best to back up all your
> > data, double-check the backup, and use two different fdisk programs
> > to record the partition locations before making any changes.
> 
> Transfer the hdd to another box followed by a full backup and
> re-partition & format was another option.  But, being fundamentally
> lazy I wanted to avoid that.

If that's the case, I hope you're prepared to lose your data.  You'll
likely get away with doing this a few times without proper backups, but
it will bite you.  Ask how I know.

> > Oh, and Googling says that the "dd bs=512" command you mentioned
> > will not, in fact, wipe the partition table, and such is my
> > recollection (though I did get burned trying to run that command
> > once before).
> 
> Interesting ... some of the links Google gave me suggested exactly the 
> opposite. :-/  (I admit to being perplexed by that since I was of the 
> understanding previously that the MBR was used for a bootloader and 
> only a bootloader, while the partition table was stored elsewhere.)

And I've now seen once reference which claimed that bytes 447 through
510 are where the partition table is stored, contradicting advice I had
earlier.  Grabbing the first 512 bytes of the disk of the laptop I'm
using right now seems to bear that out.  Even more caution is called
for, I think.

My apologies for the bad information.
-- 
Jason Parker-Burlingham
<jasonp at panix.com>
(Watch this space)