[parted-devel] [PATCH] Do not discard bootcode from extended partition

Petr Uzel petr.uzel at suse.cz
Fri Feb 20 10:53:08 UTC 2009

On Fri, Jan 23, 2009 at 02:31:01PM +0000, Bryn M. Reeves wrote:
> James Courtier-Dutton wrote:
> > I thought that valid boot sectors have a checksum or some kind of
> > signature bytes. It might be worth verifying that it is a valid boot
> > sector before blindly using it. If it is not a valid boot sector, one
> > might as well fill it with zeros.
> Which field are you thinking of here? There's the (optional) 32-bit 
> disk signature at 0x01b8 (immediately following the executable code) 
> and the 16-bit MBR signature at 0x01fe.
>  From what I can see, neither of these would be suitable.
> The disk signature is optional and is only intended to be a unique 
> identifier. The "MBR signature" is intended to signify a valid MBR but 
> it's not based on any kind of checksum - if the field contains 
> "0xaa55" it's valid, any other value and it's not.
> I just checked a bunch of devices that have valid MSDOS partition 
> tables but do not have valid boot code (removable USB devices, some 
> auxiliary HDs and a bunch of LUNs on my iscsi test box). All of these 
> had the 0xaa55 signature, but no valid bootcode at offset 0, so I 
> don't think we can use this as a check.


how could we push this forward? Is zeroing bootcode of newly
created extended partition worth the trouble?


Best regards / s pozdravem

Petr Uzel, Packages maintainer
SUSE LINUX, s.r.o.                          e-mail: puzel at suse.cz
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