Date: Sun, 18 Mar 2001 11:27:46 +0100 From: Hubert Tournier <hubert.tournier@online.fr> To: FreeBSD-gnats-submit@freebsd.org Subject: i386/25889: FDISK lost a partition ! Message-ID: <3AB48DA2.7F62060B@online.fr>
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>Number: 25889
>Category: i386
>Synopsis: FDISK lost a partition !
>Confidential: no
>Severity: serious
>Priority: medium
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Sun Mar 18 02:30:03 PST 2001
>Closed-Date:
>Last-Modified:
>Originator: Hubert Tournier
>Release: FreeBSD 4.2-RELEASE i386
>Organization:
Maison
>Environment:
I use an ASUS motherboard with ASUS P5 A-B ACPI BIOS Revision 1010 (with
support for disks over 8.4 GB).
Here is the description of the hard disk drive I'm using (from
/var/log/messages) :
ad0: 19574MB <WDC WD205BA> [39770/16/63] at ata0-master UDMA33
>Description:
SUMMARY: I lost a partition beginning after the 8.4MB limit after an
ugrade from FreeBSD 4.0-RELEASE to 4.2-RELEASE made with a complete
reinstall of the operating system.
Here was my partition information BEFORE the problem :
MBR/PT track
100 MB DOS partition
4000 MB Win partition
3992 MB FreeBSD 4.0 partition
11476 MB Win data partition (extended I think).
When I first entered FDISK, here's what I saw (from memory) :
Disk Geometry 2495 cyls/255 heads/63 sectors = 40082175 sectors (19571
MB)
Offset Size (ST) End Name PType Desc Subtype Flags
0 63 62 - 6 unused 0
63 208782 208844 ad0s1 2 fat 6
208845 8193150 8401994 ad0s2 2 fat 11
8401995 8177085 16579079 ad0s3 3 freebsd 165
16579080 23509080 40088159 - 6 unused 0
The last entry was incorrect : it should have been my 11 Go windows data
partition.
Although I was surprised, I thought the FDISK utility may have been
troubled with that partition starting after the 8.4 GB limit.
I decided to install anyway using the same parameters than the existing
FreeBSD 4.0-RELEASE partition.
The install went fine as usual, but both FreeBSD and Windows could not
see the windows data partition afterwards.
Using a disk editor, I saw that the fourth partition entry in the
partition table had been zeroed.
I think this is the only impact, but at this time, I haven't been able
to restore values enabling Windows or FreeBSD to see the lost partition.
>How-To-Repeat:
It's not possible for me to repeat the problem at this time, because I
want to try different things in order to recover the partition data.
Perhaps, on another machine, someone could try the following procedure :
- Use a disk larger than 8.4 GB,
- Create a partition layout similar to the one I was using,
- Create an extended partition beginning after the 8.4 GB limit,
- Overwrite an existing FreeBSD installation using the FreeBSD
4.2-RELEASE installer,
- See if the extended partition is still there.
>Fix:
PROPOSED MODIFICATION: In my opinion, the safest method would be to only
write back the modified partition entries in the table.
For my part, I used the FDISK utility to recreate something like that :
Disk Geometry 2495 cyls/255 heads/63 sectors = 40082175 sectors (19571
MB)
Offset Size (ST) End Name PType Desc Subtype Flags
0 63 62 - 6 unused 0
63 208782 208844 ad0s1 2 fat 6
208845 8193150 8401994 ad0s2 2 fat 11
8401995 8177085 16579079 ad0s3 3 freebsd 165
16579080 23503095 40082174 ad0s4 1 extended DOS 5
40082175 5985 40088159 - 6 unused 0
But at this time, it doesn't solve my problem (the last partition is
still unrecognised).
I plan to fiddle with the partition type, then, in last recourse, to
write a specific recovery program under FreeBSD (I already did this for
an HPFS partition in the past).
Here is my partition information AT THIS TIME :
******* Working on device /dev/ad0 *******
parameters extracted from in-core disklabel are:
cylinders=2495 heads=255 sectors/track=63 (16065 blks/cyl)
Figures below won't work with BIOS for partitions not in cyl 1
parameters to be used for BIOS calculations are:
cylinders=2495 heads=255 sectors/track=63 (16065 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 6,(Primary 'big' DOS (> 32MB))
start 63, size 208782 (101 Meg), flag 0
beg: cyl 0/ sector 1/ head 1;
end: cyl 12/ sector 63/ head 254
The data for partition 2 is:
sysid 11,(DOS or Windows 95 with 32 bit FAT)
start 208845, size 8193150 (4000 Meg), flag 0
beg: cyl 13/ sector 1/ head 0;
end: cyl 522/ sector 63/ head 254
The data for partition 3 is:
sysid 165,(FreeBSD/NetBSD/386BSD)
start 8401995, size 8177085 (3992 Meg), flag 80 (active)
beg: cyl 523/ sector 1/ head 0;
end: cyl 1023/ sector 63/ head 254
The data for partition 4 is:
sysid 5,(Extended DOS)
start 16579080, size 23503095 (11476 Meg), flag 0
beg: cyl 1023/ sector 63/ head 255;
end: cyl 1023/ sector 63/ head 254
>Release-Note:
>Audit-Trail:
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