I have 2 hard drives on my system. One (my main drive) has an
MS-DOS slice (naturally the first slice) and 3 FreeBSD slices.
The other drive had 1 OS2 slice (just because an OS2 CDROM was used
to slice it up) and 1 MS-DOS slice. At one time, I was thinking of
putting the boot program on the second hard drive, and may have done
it with the CDROM of FreeBSD 4.7 . Recently, while I was running
MS-DOS and processing e-mail (trying to remove an attachment from
a letter in order to save it in the MS-DOS slice on the second hard
drive) through juno.com , I discovered that the MS-DOS slice on this
second hard drive was hosed (naturally, that discovery could only be
made while running MS-DOS ), and verified that fact by trying to go to a
directory on that second drive. MS-DOS didn't go there but complained, and
following that I couldn't see anything on that second drive.
To investigate this, I rebooted into my FreeBSD 4.3 slice and
found that the slice-table (often called "partition-table") on the second
drive was identical to that of the first drive. In fact, when I tried fdisk
on each drive, I found the results identical except for the size (# of
cylinders) of the drives. Originally, the second drive's fdisk results
stated 3 heads and some sectors per cylinder (but I don't recall how many). I
conclude that there is a strong possibility that only the slice-table sector
has been copied (from the first drive), though I have no idea how this could
have happened (though I consider the possible putting of the boot program on
the second hard drive as possibly contributory). Does anyone have any idea of
how this can happen? Has anyone seen this or the like before?
I also conclude that there is a strong possibility that the rest of the
second disk (i.e., my data on it) is okay, and if I can rebuild the
slice-table then I can recover the rest of the disk and all my data. I think
I can do this if I can get the following things/information:
1) is there a duplicate of the slice-table
somewhere on the disk, and if so, where is it,
and how can I examine it rather than the
primary slice-table ,
and is there a way to have its contents replace
the contents of the primary slice-table ,
2) is there a program that can look at a(n entire)
disk and break it up into contiguous sectors
that belong to particular systems (in my case
OS2 or MS-DOS ), {I would be willing to write such a
program if someone would tell me how to read sectors
without a slice-table [say with just an LBA
number] and how to recognize whether a sector
belongs to OS2 or MS-DOS , and any timing
constraints for reading/writing cylinders [e.g., usual
timing for getting a read/write head to cylinder 0
, the time
to move between cylinders, etc.], if such
constraints exist [maybe we have fixed heads
and so no timing constraints]},
3) FreeBSD programs (or Linux programs or
MS-DOS programs if FreeBSD programs aren't
available) that can read any sector given its
LBA number or the like [somewhat like fdisk
reads/writes of sector 0 ], what could be really
useful [if I have to rebuild files] is a program that
reads a range of sectors and greps its contents,
reporting the LBA
number [and some contents] of those sectors
that pass the grep test,
4) the structure of the slice-table's sector and
of the slice-table and FreeBSD programs
that can write specific values (given as
arguments [say in structures]) into the
slice-table without affecting the contents of any
other sector on that disk,
5) how to mark a slice "<UNUSED>",
6) FreeBSD programs (or Linux programs or
MS-DOS programs if FreeBSD programs aren't
available) other than fdisk that can write
the slice-table's sector (including its magic number
and boot code) without affecting the contents of
any other sectoron that disk,
7) how can I recognize sectors that were in a
slice assigned for MS-DOS usage, and/or is
there a way of finding the "first" (i.e., one
with lowest LBA ) and "last" sector assigned for
MS-DOS usage or used by MS-DOS ,
8) FreeBSD programs (or Linux programs or
MS-DOS programs if FreeBSD programs aren't
available) software to rebuild files and
[Windows-98] directories from fragments (with human
direction) [this is just in case there is more damage
than I suspect at present,
I'm hoping not to need this one],
9) any caveats or information that would prove
useful in this endeavor.
If I have to rebuild the slice-table from scratch, I presume that I
can make any entries I wish in the slice-table and then look at the contents
of the slices to see if they are what I would like to find there and
appropriately change the slice-table until I find it set up as it was before.
Anything wrong with my presumption?
If I succeed in this, I'm thinking of publishing an article on how to
recover from this sort of problem.
uname -a for my system gives:
FreeBSD 4.3-RELEASE FreeBSD 4.3-RELEASE #0: Sat Apr 21 10:54:49 GMT 2001
[EMAIL PROTECTED]:/usr/src/sys/compile/GENERIC i386
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