linux-ext4 - Re: Corrupted superblock? But disk still mounts.

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Date:	Fri, 22 Aug 2014 17:40:02 +0100
From:	Mark Ballard <markjballard@...glemail.com>
To:	Eric Sandeen <sandeen@...hat.com>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: Corrupted superblock? But disk still mounts.

No, Eric. I can see it's accurate in its own context. I mean accurate
in relaying enough information to convey the situation accurately to
the user. That requires something like e2label to see a wider context,
and I can see that might actually be an unreasonable expectation. But
this is what I was getting at: information accurate enough to allow
non-educated users to get an instant grip of the environment when they
are forced to go delving under the bonnet (hood) of their computer.
None of the os componenets were made -- or documented -- with that
sort of user in mind: someone with less time and experience than is
really required to work efficiently under there. Yet the application
environment is such a tangle that users are left with little choice
but to get their hands dirty. And when you look under there, you see
that it was made by Heath Robinson but that the drawings were burned
in a fire.

On 22 August 2014 17:09, Eric Sandeen <sandeen@...hat.com> wrote:
> On 8/22/14, 9:19 AM, Mark Ballard wrote:
>> Ya. It did look that way. 'Scuse me for not checking first.
>>
>> But my point is that it may still be a problem for ext4, dumpe2fs,
>> e2fsck, fsck and presumably gparted and so on.
>>
>> That is, would it not be polite of them to report the error ...<drum
>> roll>... accurately?
>
> Ah, I see.  So you don't like "corrupted" - you'd like to know that it's
> something else perfectly valid, just not the thing you were looking for.
>
> Maybe like:
>
> # misc/dumpe2fs /dev/sdc1
> dumpe2fs 1.43-WIP (09-Jul-2014)
> misc/dumpe2fs: Superblock checksum does not match superblock while trying to open /dev/sdc1
> Couldn't find valid filesystem superblock.
> /dev/sdc1 contains a xfs file system
>
>
> # misc/dumpe2fs /dev/sdc
> dumpe2fs 1.43-WIP (09-Jul-2014)
> misc/dumpe2fs: Superblock checksum does not match superblock while trying to open /dev/sdc
> Couldn't find valid filesystem superblock.
> /dev/sdc is entire device, not just one partition!
>
> -Eric
>
>> (No irony intended.)
>>
>>
>> On 19 August 2014 15:36, Eric Sandeen <sandeen@...hat.com> wrote:
>>> On 8/18/14, 3:23 PM, Mark Ballard wrote:
>>>>> I'm guessing that it's the encryption getting in your way.
>>>>
>>>> Cheers, Eric. Does rather look that way. But for the sake of a user report...
>>>>
>>>>>
>>>>> How is /dev/sdb1 encrypted?  Usually this is done with something like dm-crypt.
>>>>> Or is it hardware encryption managed in the bios?  Did you unlock it?
>>>>
>>>> Done with crytpsetup using luks.
>>>>
>>>>>
>>>>> What does "blkid /dev/sdb1" say?
>>>>>
>>>>
>>>> It says Luks.
>>>
>>> and not ext4 - so you need to unlock it via mumblemumbleLuksStuffmumblemumble
>>> before you can operate on it with e2fsprogs tools.
>>>
>>> # cryptsetup luksOpen /dev/sdb1 <name>... or something.  Sorry, I'm not a LUKS
>>> expert...
>>>
>>> Anyway, not an ext4 problem.  Your superblock isn't corrupted, it's encrypted.  :)
>>>
>>> -Eric
>>>
>
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