Re: [dm-crypt] Device $dev is not a valid LUKS device.

[Erik Logtenberg <erik@logtenberg.eu>]

Hi Arno,

Do you have some pointers on how I can investigate that?

In my previous setup, I had my luks device directly on top of my iscsi
device. That worked great in the beginning, but after a power failure on
the iscsi server, my volume was destroyed. Since the luks device was the
only contents on the iscsi device, there was not much
testing/investigating that I could do.

So I changed the setup: I created an LVM volume on my iscsi device, and
the luks device inside the LVM volume. That way, I thought, I would at
least know what part of the setup caused the malfunction. I mean, if the
iscsi device itself would become corrupted, I wouldn't be able to
activate the LVM volume anymore, but if dm-crypt were to make some
mistake, I would expect to still be able to activate the LVM volume, but
then not be able to read the luks volume.

Right? Well, it turns out I can still activate the LVM volume just fine,
so apparently there are no media errors / overwritten headers, at least
no overwritten LVM headers.
But then, after I activated the LVM volume, dm-crypt can't read the luks
volume. So apparently -only- the luks volume is damaged in some way.
So... how can I investigate this further?

Kind regards,

Erik.


On 03/04/2013 03:04 PM, Arno Wagner wrote:
> Hi Erik,
> 
> first, you can make a header-backup, see the FAQ. Second, you can 
> investigate what destroys the header. The same thing could
> well destroy a filesystem, RAID-superblock, etc.
> Or put differently: Something is very, very wrong in
> your set-up. Loss of the LUKS header can only happen if
> einther the user does it (directly or indirectly) or
> somethign is broken. 
> 
> Arno
> 
> On Mon, Mar 04, 2013 at 01:58:31PM +0100, Erik Logtenberg wrote:
>> Hi all,
>>
>> I've been using dm-crypt for quite some years now, and every now and
>> then I am very unpleasantly surprised by the message that my entire
>> volume can no longer be read:
>>
>> Device /dev/disk/by-path/ip-foo.bar:mainstorage-lun-1 is not a valid
>> LUKS device.
>>
>> In this case the iscsi server was rebooted while the volume was still
>> mounted. The volume is used for making backups and no backups were
>> currently made, so no actual writes got lost. Nevertheless after reboot
>> it no longer recognizes my luks volume.
>>
>> I've had this kind of malice before and at that time was unable to fix
>> it. So in the end I gave up, created a new luks volume and started from
>> scratch.
>>
>> However I hope that is not how every future power failure is going to
>> end up. Is there anything I can do to fix this volume or anything I can
>> do to prevent such a simple event from causing such catastrophic results?
>>
>> Kind regards,
>>
>> Erik.
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>