China DOS Union

Sender: netwolf (Little Wolf), Board: DOS
Title: The junior girl apprentice finally smiled (repost)
Post site: BBS Shuimu Tsinghua Station (Wed Oct 15 10:29:36 1997)

【 The following text is reposted from the SGI discussion board 】
【 Originally posted by gddx 】
For the past few days, the junior girl apprentice had been looking worried,
just because a few days ago she fdisk'ed my machine,
and nearly ruined my three years of doctoral dissertation work.
Thanks to the enthusiastic help of all the users on the board, the machine after fdisk
has finally returned to normal.

*******************************
First we took a new hard drive and repeated the junior girl's mistake once. Then we used NDD to diagnose it,
and the original partition table was completely restored. The data could be copied normally. ㄊγ迷趂disk时只是删除了
drives D and E, and did not create a new partition).
Then we handled the original hard drive with exactly the same plan, and the data was restored.
Afterward, repartition the hard drive again; as long as you do it according to 'partition H to the original size and then use NDD to diagnose, the data is restored.
:
LLLLLLLLLLL

--
※ Modified by ·netwolf at Oct 15 10:30:54 modifying this post·
※ Source: ·BBS Shuimu Tsinghua Station bbs.net.tsinghua.edu.cn·

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First, congratulations to that brother whose doctoral dissertation was finally saved. It seems FDISK is not all that evil. Today I also tested the effect of FDISK on my own machine, and the results were as follows:

1 Originally there were three drives, C, D, and E. I used FDISK to delete drive E, but did not rebuild it. Using DISKEDIT to inspect it, I found that E's partition table
and BOOT sector were preserved intact; of course the FAT and so on were all still there;

2 I used FDISK to rebuild drive E, but did not format it. Using DISKEDIT to inspect it, I found that E's BOOT sector had been completely filled with F6,
while the rest of the information was intact;

Actually this is reasonable, because after rebuilding E, FDISK naturally assumes that the original BOOT sector also needs to be rebuilt, so it fills it with
F6. Otherwise the original BOOT sector would become valid. After rebuilding E, if you overwrite it back with the E BOOT sector you saved earlier,
then E is completely restored to its original state, and all the files inside are OK. Of course if you rebuild E and then FORMAT
it, then there's no way, unless you backed up the original FAT and root directory table.

--
Having walked to the ends of the earth, in the end I still turn back
After seeing flowers like a sea, they fall like snow


※ Modified by ·microbe at Oct 15 14:01:21 modifying this post·
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Sender: microbe (Wonderful Microbe), Board: DOS
Title: Supplement to the FDISK experiment
Post site: BBS Shuimu Tsinghua Station (Thu Oct 16 19:43:22 1997)

【 In quene (Qinling)'s post it was mentioned: 】
: Generally speaking, FDISK does not just fill the BOOT sector with the F6 marker; it also fills some sectors in the data area with
: the same marker.

Thanks for the reminder. I tried once more and found that it really is as you said: it doesn't just fill the BOOT sector with the F6 marker.
In fact, in the cylinder where partition E begins, the first sector of heads 1 through 15 was all filled with F6, so of course it wasn't
just the data area anymore; the FAT and RDT were also damaged. In the previous experiment I didn't realize that FDISK writes in jumps like that.
Of course this happens after rebuilding the partition with FDISK; merely deleting the partition will not fill with F6.

--
Having walked to the ends of the earth, in the end I still turn back
After seeing flowers like a sea, they fall like snow


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Sender: microbe (Wonderful Microbe), Board: DOS
Title: Re: Urgent Help: Can FDISK be recovered?
Post site: BBS Shuimu Tsinghua Station (Sat Oct 11 19:19:29 1997)

I think the odds are bad.
The partition table is manageable, but the key is that your original partition's BOOT sector and FAT table are gone, because when FDISK repartitions,
it rewrites the first few (seems like 3) cylinders at the start of the partition to 0 — that's from an original edition book I read, though it may
apply only to lower DOS versions.
I suggest you do the following:
1 Restore the original partition table (using DISKEDIT);
2 Before formatting the partition, use DISKEDIT to save that partition's FAT tables (both copies) and root directory table to a floppy disk;
3 Quick-format that partition, i.e. FORMAT/Q, not FORMAT;
4 Write back the FAT tables and root directory table that you saved (if you find the two FAT tables differ, it's possible the first FAT table
has already been damaged; in that case use the second copy as the standard; if the second one is also ruined, then it's very troublesome);
5 Boot from a floppy again and see whether all your files are still there and whether they can be read;
6 If they cannot be read, that proves the FAT table has already been damaged. At that point don't install anything onto the hard drive yet; use NORTON's TS
(Text Search) to search (you need to provide keywords from your dissertation). For the specific usage, read HELP.
Whether it can be recovered depends on your luck.

The key is whether the FAT can remain intact.

--
Having walked to the ends of the earth, in the end I still turn back
After seeing flowers like a sea, they fall like snow


※ Modified by ·microbe at Oct 14 19:44:40 modifying this post·
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: Brothers and sisters, please come save me quickly.
: I am waiting for the savior who can save my life.

There is still a glimmer of hope:
But you must know some of your hard drive's previous data, such as the partition layout of each drive, the main directory structure, etc.

If your hard drive had only one primary partition, then it's easier. You only need to repartition the drive back into its original state,
(do not format it no matter what!!!), then on a floppy use NORTON (for a WIN95 drive you must use NORTON95) DISKEDIT,
read a DOS boot record from another machine, and overwrite it onto your hard drive (Cyl:0,Head:1,Sect:1),
then according to your hard drive's partition table data find the total number of sectors on the hard drive, and calculate the number of sectors in the FAT,
finally modify those two corresponding data items in the DOS boot record, and then quickly back up your data!

If your hard drive partitioning is relatively complicated, and your files are not in the primary partition, then it's much more troublesome. I hope
you're not that unlucky.

If anything is still unclear, please write to contact me. Also, you absolutely must be careful when repairing it, otherwise one wrong
operation may make your hard drive impossible to save!

Finally, good luck. I really do sympathize with you.


--
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: When partitioning, try your best to keep each logical drive the same size as before. For example, if drive C used to be 200M, then now
: create a 200M C drive again. Then read drive C and see whether you can find your data.
: By using FDISK multiple times to make suitable adjustments to the logical drive sizes, it should be recoverable. I succeeded
: once. It's very troublesome, but it won't take five months, :p. But do be careful, you must not write to the hard drive,
: otherwise....
: gOOD LUCK
//shout Absolutely don't listen to him!! Unless he agrees to find it for you!! (His method isn't impossible, it's just super troublesome!!)

A simpler method: use norton's diskedit, bring up the primary partition (physically read hard disk 0 0 1)
then change it back to your original state. (If you don't remember, you can use diskedit's search function
to look for the PARTITION TABLE. Then you may also need to manually restore the DOS master boot sector. I think
someone posted the structure of that sector earlier. Basically recovery can succeed this way, as long as you operate carefully.
If you have a rescue disk, then just rescue directly. (I suggest everyone make
a rescue disk)
--
Boeing 747: It's 2M microwaves now, how does it feel?
Space shuttle: Still not enough, brother, add a bit more fuel.
_|_
__^|^__
---0==0__O__0==0---

※ Modified by ·ghosts at Oct 12 02:01:30 modifying this post·
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Use SPFDISK to repartition it according to the original partition layout; just choose non-destructive partitioning.

An even safer method is to have her take the hard drive to an antivirus company. This kind of problem is no problem at all for the technicians at an antivirus company. (Though of course there may be a bit of labor charge.)