Dangerous file system / disk problem

[Dan Strick]

On Sun, 6 Jun 2004 19:31:48 +0100, Ben Paley wrote:
>>
>   ...
>
> ******* Working on device /dev/ad1 *******
> parameters extracted from in-core disklabel are:
> cylinders=155061 heads=16 sectors/track=63 (1008 blks/cyl)
>
> Figures below won't work with BIOS for partitions not in cyl 1
> parameters to be used for BIOS calculations are:
> cylinders=155061 heads=16 sectors/track=63 (1008 blks/cyl)
>
> Media sector size is 512
> Warning: BIOS sector numbering starts with sector 1
> Information from DOS bootblock is:
> The data for partition 1 is:
> sysid 165 (0xa5),(FreeBSD/NetBSD/386BSD)
>     start 63, size 156296322 (76316 Meg), flag 80 (active)
>         beg: cyl 0/ head 1/ sector 1;
>         end: cyl 1023/ head 254/ sector 63
> The data for partition 2 is:
> sysid 14 (0x0e),(Primary 'big' DOS (>= 32MB, LBA))
>     start 156296385, size 0 (0 Meg), flag 0
>         beg: cyl 1022/ head 0/ sector 1;
>         end: cyl 1022/ head 254/ sector 63
> The data for partition 3 is:
> <UNUSED>
> The data for partition 4 is:
> <UNUSED>
>
>   ...
>
> I don't really understand this, frankly: it certainly gives the right 
> partition type code for the main partition, but I'm not sure of the relevance 
> of the other stuff... does it look ok to you? Or is this "partition 2" where 
> the problem is? Partition Magic in Windows sees only one partition on that 
> disk. The slice editor in sysinstall shows this for ad1:
>
>   ...
>
> 5.2-CURRENT. But BSD sees everything ok, it's Windows that's having a
> problem. I don't feel confident making any changes in Windows, however,
> because it seems as though my only option there would be to format the
> partition! Which, from a Windows point of view, would certainly be a
> solution of sorts...
>>

Partition 2 (sysid 14, start 156296385) is bogus.  I don't have a clue as
to how it might have been created.  If the beginning/end c/h/s addresses
are to be believed, it overlaps partition 1.  I would not dare to format
it.  Instead, I would use the "fdisk -u ad1" command to delete it and
hope that it never comes back.  If you do this, it would be a good idea
to back up your FreeBSD system first, especially since you are probably
not very familiar with the "fdisk -u" command and might possibly make a
fatal mistake.

Dan Strick