Re: A couple of questions

[Manuel Krause <manuelkrause@netscape.net>]

On 05/17/2002 02:45 AM, Philipp Gühring wrote:

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> Dear Hans,
> 
> 
>>I am a filesystems developer, and I don't know enough to do more than
>>press y with most fscks.  
>>
> 
> There is one case, in which I know that I have to say no: If the partition 
> that a fsck tries to correct has a different type than the fsck thinks. 
> (Running e2fsck against a reiserfs partition for example)
> 
> And those things happens when someone changes harddisks, ...
> 
> 
>>I think that for the most part, if one is
>>going to ask the user to help, one needs to provide a real interface, a
>>filesystem structure editor.....  
>>
> 
> Well, debugfs (ext2) was an approach into that direction, isn't it?
> Now I stumbled across debugreiserfs, but it lacks interactive mode.
> 
> 
>>which no FS has ever done....  but
>>right now we need to get what we have debugged thoroughly.  It is on the
>>list of things I would like to add someday.
>>
> 
> What I would like to see is a tool to do the following:
> (And I don't think that I will find a sponsor for that tool :-(
> 
> After a crash, I make a dd from the crashed partition, into a normal file in 
> another partition, that's perhaps on a differnt harddisk.
> 
> Then I want to run a dumping utility, that tries to restore every bit that 
> still can be found in the crashed partition, and tries to resemble all the 
> files in it, and even creating a lost&found directory ...
> 
> That dumping utility should take an output directory as argument, in which it 
> recreates the contents.


It should take a FILE of the SAME size of the original partition as 
output. So the utility or user may dd it back safely.

> 
> Something like "The Coroners Kit", but more for rec2overy than for 
> investigation.
> 
> What is important for that tool:
> * It must not crash under any circumstances. Even if every bit of the 
> filesystem is currupted, it has to do its work, and try to recover as much as 
> possible.
> * It has to assume that every bit of the filesystem can be corrupt, so it has 
> to try to semantically verify the bits, pointers, ...
> * It should try different ways to restore access to lost data, if it stumbles 
> across problems in the filesystems.
> * There must not be any assertions that would not allow the tool to run over 
> the whole partiton, and search everywhere for lost data
> * It has to be designed to work on files which are dumps from partition based 
> filesystems.
> * It should be able to detect and correct common hardware or crash related 
> problems in the filesystem: 
>   * Files that are not statable or accessible, because there only exists an 
> entry in the directory, but nothing in the reiserfs tree
>   * Transactions that are open
>   * Corrupted directory entries like filenames with special charakters that 
> can not be used from the system, or rights with undefined bits, ...
>   * ...
> * It must not change any data on the partition, instead it writes everything 
> to an output directory


...FILE, that is able to be checked manually via loop-mount to see the 
difference... Philipp is very right on his needs. We all are interestedm 
I assume.

> 
> Many greetings,
> - -- 
> ~ Philipp Gühring              p.guehring@futureware.at
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Best wishes,

Manuel