From: Mark Ballard <markjballard@googlemail.com>
Subject: Re: Corrupted superblock? But disk still mounts.
Date: Fri, 22 Aug 2014 19:21:26 +0100
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Cc: linux-ext4@vger.kernel.org
To: Eric Sandeen <sandeen@redhat.com>
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On 22 August 2014 18:20, Eric Sandeen <sandeen@redhat.com> wrote:
> On 8/22/14, 11:40 AM, Mark Ballard wrote:
>> 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,
>
> so saying something like:
>
> "invalid superblock.  This is an xfs filesystem."
>
> isn't sufficient?  And here I thought that was a great idea ;)
>
> I'm not sure how much further we could reasonably go in error messages...
>
> At some point we have to assume some degree of administrative skill and
> familiarity...

Yes and there's no accounting for the stubborn incontinence of a user
making indignant forays under the bonnet.

It did seem reasonable to me for a moment that these disk utilities
would say, e.g. ... can't operate on encrypted file system'. But I see
how that might not be a reasonable expectation.

The alternative is that users have to think. That's a big ask!-) ...
They've got other things to think about.

Mark.

>
> -Eric
>
>> 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@redhat.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@redhat.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
>>>>>
>>>
>