Re: [gentoo-user] The sudden disappearance of ....WHAT??? (I/O error on a SD flash card?!)

[Bill Kenworthy]

On 26/03/17 15:26, tuxic@××××××.de wrote:
> On 03/26 03:04, Bill Kenworthy wrote:
>> On 26/03/17 14:25, tuxic@××××××.de wrote:
>>> On 03/26 05:50, tuxic@××××××.de wrote:
>>>> On 03/26 11:21, Adam Carter wrote:
>>>>> Step 1: dd the contents into an image
>>>>>
>>>>> ddrescue is probably a better option than plain dd.
>>>>>
>>>>> step 2: put the sdcard to one side.
>>>>>> step 3: loopback mount a copy of the image (not the original)
>>>>>> step 4: try recovering the filesystem on the loopback, if it fails ... try
>>>>>> something else on another image copy
>>>>>
>>>>>
>>>>> Yep, once you've got the image mounted loopback, you can run
>>>>> testdisk/photorec depending on how bad it is.
>>>>
>>>> Hi all,
>>>>
>>>> thanks a lot for all help! :)
>>>>
>>>> Currently I am ddresucueing the flashcard to the harddisc.
>>>> Next I will try to mount the sdcard.
>>>>
>>>> What reliable sdcard-reader can one recommend ?
>>>> (...sorry if this sentence sounds harsh...I it by no means meant
>>>> that way...I am no native speaker... :)
>>>>
>>>> Cheers
>>>> Meino
>>>>
>>>>
>>>
>>> Hi,
>>>
>>> Is the assumption correct, that -- if ddrescue could read each
>>> partitions of the sdcard without stuttering, retries and errors --
>>> the sdcard itsself is ok and "only" the logical structure
>>> (fs, superblock etc) got damaged?
>>> Or do I overlook something?
>>>
>>> (Background: I dont want to put a sdcard into the bin, if
>>> fdisking & reformatting that beast would gives me back an ok
>>> media...)
>>>
>>> Cheers
>>> Meino
>>>
>>>
>>>
>>>
>>
>> The dd gets you the best chance to work on the data before it completely
>> fails.  In my experience the sdcard will only get worse ending with total
>> failure - if it hasn't already.
>>
>> If the dd dump comes up rubbish and cant be recovered, the actual sdcard
>> will be worse.  You can run "strings" against the image to see if there is
>> any text in there (or even cat the /dev/sdcard node through strings) to see
>> if the bits are still there.
>>
>> I dont know of a cdparanoia type recovery utility for sdcards but I suspect
>> sdcard design means that approach wont work.
>>
>> BillK
>>
>>
>>
>
> Hi Bill,
>
> I got mixed results: There are three partitions on the sdcard from
> which I could fully recover (even mount it directly via loop device)
> the first and the third one.
>
> The second one is screwed up.
>
> Running fsch.ext4 against the image it starts with "bad superblock"
> and suggests two alternatives.
>
> I started fsch.ext4 again while using -b to define the alternate
> superblock and it starts to ask me *zillions of question, which
> I all answered with 'yes' in a first attempt (I have a backup of the
> image...).
> The result was an image, which I could mount again.
> But beside 'lost+found' with some small rests of something which
> may be files in a previous life nothing was there....
>
> Currently it looks to me, that something has totally messed up the fs
> there.
>
> What do you think?
>
> Cheers
> Meino
>
>
>
>
>
Sounds like its toast :(

I have never had a lot of luck with any of the ext file systems - you 
have to baby them and they corrupt very easily compared to others.  I 
try and avoid them ...

BillK