MBR was destroyed

Saulius Krasuckas saulius2 at ar.fi.lt
Mon Nov 21 04:34:11 CST 2005


* On Sun, 20 Nov 2005, seorge wrote:
> 
> As a regular user I've launched winecfg as a regular user, then 
> proceeded to the dist setup. I've tried several options like automatic 
> configuration, manual configuration. Then I've tried to change some 
> drive letters manually. After reboot a "PRESS A KEY TO REBOOT" message 
> appeared instead of a GRUB screen.

It would be very helpfull if you will find minimal winecfg operation, 
which destroys MBR.

* On Sun, 20 Nov 2005 wino at piments.com wrote:
> 
> You should probably try to reproduce this in a more controlled way to 
> establish that it was wine that removed grub.

Yeah, right.
Seorge, may you repeat the process of wiping and restoring lots of times? 
I guess other devs don't like to risk on this. :-P

I think it would usefull to know:
- whether MBR is wiped by setting some properties in wincfg or just by 
  retrieving them (to look at for)?
- creating what link in ~/.wine/dosdevices dir is fatal to the MBR?  Is it 
  sufficient to setup only C: (manually, in a way as you did) for that?

You may run dd command to retrieve MBR at every moment, calculate it's 
checksum and see whether it differs or not.  I'd do this way:

$ dd if=/dev/hda of=./hdd.mbr bs=512 count=1
| 1+0 records in
| 1+0 records out
$ dd if=/dev/hdd of=./hdd.mbr bs=512 count=1
| 1+0 records in
| 1+0 records out
$ md5sum *.mbr
| bc92a20f6c2c5795635108b000fa1ec0  hda.mbr
| e0474e52eca44ebf9389ef3e263e6936  hdd.mbr
$ cat hda.mbr | od -t x1 | head -n 5
| 0000000 eb 48 90 d0 bc 00 7c fb 50 07 50 1f fc be 1b 7c
| 0000020 bf 1b 06 50 57 b9 e5 01 f3 a4 cb be be 07 b1 04
| 0000040 38 2c 7c 09 75 15 83 c6 10 e2 f5 cd 18 8b 14 8b
| 0000060 ee 83 c6 10 49 74 16 38 2c 74 f6 be 10 07 03 02
| 0000100 ff 00 00 80 20 74 4a 04 00 08 fa ea 50 7c 00 00
$ cat hdd.mbr | od -t x1 | head -n 5
| 0000000 33 c0 8e d0 bc 00 7c fb 50 07 50 1f fc be 1b 7c
| 0000020 bf 1b 06 50 57 b9 e5 01 f3 a4 cb be be 07 b1 04
| 0000040 38 2c 7c 09 75 15 83 c6 10 e2 f5 cd 18 8b 14 8b
| 0000060 ee 83 c6 10 49 74 16 38 2c 74 f6 be 10 07 4e ac
| 0000100 3c 00 74 fa bb 07 00 b4 0e cd 10 eb f2 89 46 25

It would be interesting to see, what stays in MBR after it is overwritten.  
Maybe try comapare hexadec outputs between themselve:

$ diff -u hda.txt hdd.txt


* On Sun, 20 Nov 2005, seorge wrote:
> 
> Next time I booted with grub-floppy and then restored the MBR with 
> grub-install /dev/hda.

* On Sun, 20 Nov 2005, Andreas Mohr wrote:
> 
> Whatever will happen during this discussion (hopefully this problem will 
> get fixed!), you should definitely install a new MBR there and then run 
> a Linux boot CD with something like testdisk or similar (qparted or so?) 
> on it in order to restore a proper partition table in your first HDD 
> sector...

I think Seorge did something like that already before your msg, Andreas. 
:-P



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