On Fri, Jun 08, 2007 at 10:41:40PM -0400, Kenneth R Westerback wrote:
> This is very odd on several fronts. First, someone has obviously
> been writing on the MBR for no good reason. I just tested an fdisk
> compiled to day and noticed no oddities on my i386.
>
> Second, the fact that you find a disklabel. Since we no longer store
> or look for disklabels in FreeBSD partitions it is being
> read from sector 1 if I recall the code correctly. But it should not
> have been writing the disklabel there when there was an OpenBSD
> partition to store it in.
>
> Do you know if this is exactly the same disklabel you were using
> before? Have you changed anything in the disklabel recently that
> would identify this as an artifact that just happened to be lying in
> sector 1 for a while?
Other than reducing the size of the last partition a couple of months
ago, there has been no (intentional) change to that disklabel since:
> On Wed, Oct 11, 2006 at 08:09:08AM -0700, K WESTERBACK wrote:
> > Darn. A perfectly good theory shot to hell. :-).
> >
> > It would seem that you have a 'valid' disklabel at
> > sector 1 of that disk.
> >
> > First, if you could save the first two sectors of the disk
> > with
> >
> > dd if=/dev/rsd1c of=SaveMySectors bs=512 count=2
> >
> > and send me that file, and do two experiments, I would
> > appreciate it.
> >
> > If you can run fdisk against the disk and change the partition
> > type to 'A6' (OpenBSD) the correct disklabel should be read
> > in and you should get the 'old' info back again.
> >
> > Second, if you are the risk taking type, change partition type
> > back to 'A5' (FreeBSD) and zero out sector 1 on the disk with
> > something like
> >
> > dd if=/dev/zero of=/dev/rsd1c bs=512 count=1 seek=1
> >
> > Then see what disklabel says. You should get a simple
> > spoofed disklabel with 'c' and 'i' partitions.
> >
> > Finally, changing the partition type to 'A6' again should give
> > you access to the data.
That was the last change I'm aware of.
> Can you copy the MBR and send it to me. There might be a clue as to
> what overwrote it. Then I would do "fdisk -i" and see what happens.
> This will move the OpenBSD partition to partition 3, but cover the
> entire disk as your original MBR did. Then see if the disklabel,
> which should be read from the OpenBSD partition says.
I'll send the file attached to the next message, since I assume it would
be stripped from the mailing list.
After running fdisk -i sd1:
# fdisk sd1
Disk: sd1 geometry: 4462/255/63 [71687370 Sectors]
Offset: 0 Signature: 0xAA55
Starting Ending LBA Info:
#: id C H S - C H S [ start: size ]
------------------------------------------------------------------------
0: 00 0 0 0 - 0 0 0 [ 0: 0 ] unused
1: 00 0 0 0 - 0 0 0 [ 0: 0 ] unused
2: 00 0 0 0 - 0 0 0 [ 0: 0 ] unused
*3: A6 0 1 1 - 4461 254 63 [ 63: 71681967 ] OpenBSD
It's back as an OpenBSD disklabel, but the c partition still starts at
63 rather than 0:
# disklabel sd1
# Inside MBR partition 3: type A6 start 63 size 71681967
# /dev/rsd1c:
type: SCSI
disk: da0s1
label:
flags:
bytes/sector: 512
sectors/track: 63
tracks/cylinder: 255
sectors/cylinder: 16065
cylinders: 4462
total sectors: 71687370
rpm: 3600
interleave: 1
trackskew: 0
cylinderskew: 0
headswitch: 0 # microseconds
track-to-track seek: 0 # microseconds
drivedata: 0
15 partitions:
# size offset fstype [fsize bsize cpg]
c: 71681967 63 unused 0 0 # Cyl 0*- 4461
d: 2104452 63 4.2BSD 2048 16384 132 # Cyl 0*- 130
e: 8385930 2104515 4.2BSD 2048 16384 328 # Cyl 131 - 652
f: 23294250 48387780 4.2BSD 2048 16384 328 # Cyl 3012 - 4461
h: 4112640 15936480 4.2BSD 2048 16384 256 # Cyl 992 - 1247
i: 2104515 40933620 4.2BSD 2048 16384 1 # Cyl 2548 - 2678
j: 18828180 20049120 4.2BSD 2048 16384 328 # Cyl 1248 - 2419
k: 5349645 43038135 4.2BSD 2048 16384 16 # Cyl 2679 - 3011
l: 2056320 38877300 4.2BSD 2048 16384 128 # Cyl 2420 - 2547
m: 2104515 10490445 4.2BSD 2048 16384 132 # Cyl 653 - 783
n: 2056320 12594960 4.2BSD 2048 16384 1 # Cyl 784 - 911
Emilio
