I think that is what happend to me (twice) with freedos instalation very
long ago. Ofcourse at the time no-one could help me and the problem is
non-reproductible because it fixes itself!
I vote against this and ih favor of some warning message so that the MBR
only gets written in the end if something is modifiead.
Good catch, thanks,
Alain
PS: bellow is a "Jeremy had a patch" is this included in the ibiblio or
documented ???
Eric Auer escreveu:
>> EA> You said that the "if no MBR 55aa found, replace ALL code and
>> EA> partition data in the MBR with an empty MBR" function in FDISK,
>> EA> which has caused a lot of data loss in the past, would be
>> EA> necessary to handle wiped / new / virtual harddisks properly.
>> EA> Who would like to help me to find a better solution, for
>> EA> example using his virtual computer?
>>
>> May you specify problem more precise?
>>
>> 1. Does this mean, that currently FDISK automatically wrote own MBR with
>> empty partition table, when it finds "no signature"? If yes, this is
>> bug - FDISK should ask before any write to disk (on exit from it).
>
> /* Create Master Boot Code if it is not present */
> void Create_MBR_If_Not_Present()
> {
> Read_Physical_Sectors(0x80,0,0,1,1);
>
> if( (sector_buffer[0x1fe]!=0x55) && (sector_buffer[0x1ff]!=0xaa) )
> {
> Create_MBR();
> }
> }
>
> This is called very early in
>
> void Interactive_User_Interface(),
>
> right after Ask_User_About_FAT32_Support,
> without asking the user. Several users
> have lost their boot loader, some even
> their partition table (see below),
> because Create_MBR_If_Not_Present fails
> to check for Read_Physical_Sectors errors.
> It just trusts the buffer contents. Oops.
>
> Even if it WOULD check for errors, it is
> still a very bad idea to automatically
> jump to Create_MBR: That function again
> reads the MBR, inserts the CODE and the
> signature, but leaves the partition table
> untouched.
>
> The problem is that "read error plus
> code fixed plus partition table left as
> is plus write changes back to disk" in
> the end means that the partition table
> will be destroyed.
>
> Only humans should be allowed to judge
> whether their MBR actually has to be
> rewritten. In the particular cases,
> there were troubles with disk access,
> and users would have noticed that FDISK
> had those and would have aborted rather
> than using FDISK in that situation.
>
> Another issue is that Linux still tends
> to use the MBR to store part of the boot
> menu (I usually tell it to use the Linux
> partition for that instead, but the
> default still often is using the MBR),
> so even replacing only the CODE part of
> the MBR is a bad idea when done without
> user interaction...
>
>
> My suggestion is simple: Do not modify
> any MBR contents without explicit request
> from the user. Or, if you have to present
> suggestions for changes, at least ask the
> user for confirmation...
>
>
>> EA> - it should NEVER be the
>> EA> case that FDISK automatically kills my MBR.
>>
>> Yes.
>
> Eric
>
>
> PS: I think Jeremy had a patch to make the
> harddisk detection in fdisk more lbacache style,
> and Blair also did use that patch for the
> current fdisk version on the iso. One bug less,
> fewer cases of "FDISK finds no disks".
>
> PPS: See also bug numbers 960, 1056, 1095, 1197,
> 1760 on the list:
> http://www.freedos.org/bugzilla/cgi-bin/buglist.cgi?query_format=specific&bug_status=__open__&product=Fdisk
> Bugs 1452, 1738, 1740, 1792, (1827), 1838, (1858)
> and 1899 are probably unrelated FDISK bugs.
>
>
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