Date:	Fri, 22 Aug 2014 12:20:19 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	Mark Ballard <markjballard@...glemail.com>
CC:	linux-ext4@...r.kernel.org
Subject: Re: Corrupted superblock? But disk still mounts.

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...

-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@...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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