[dm-crypt] LUKS header always disappears after reboot

Arno Wagner arno at wagner.name
Fri Jan 6 10:37:35 CET 2012

On Thu, Jan 05, 2012 at 08:11:31PM -0500, Cory Coager wrote:
> On 01/05/2012 03:11 AM, Arno Wagner wrote:
> > Well, that is not a LUKS header, that looks like an EFI MBR
> > or bootsector. There is no trace of the LUKS header.
> >
> > Either something is writing this to your disk
> > or, if this is an USB disk, the USB-to-SATA controller in
> > the disk may be doing this in violation of the spec, probably
> > in a misguided atempt to make this thing usable under Windows.
> >
> > Is this really /dev/sdb1 and not /dev/sdb and is the partition
> > still there?
> >
> > As to your data, unless you have a LUKS header backup, it is 
> > very likely gone. 
> >
> > Here is something you can try: Zero the first GB or so of
> > the drive, sync, reboot and see whether anything is on it.
> > Then do the same, but unplug the drive while the computer
> > is on and hotplug it after booting. And finaly do the same
> > and unplug and replug the drive without booting the computer.
> > That could give indication of whether the drive is doing 
> > something by itself or whether the PC is writing something. 
> >
> > Arno

> OK, I have a good deal of information of what the problem is.  The issue
> seems to happen on two specific computers but not a third.  They aren't
> recognizing the entire hard drive size.  fdisk is showing 3tb for
> /dev/sdb but if I run fdisk on /dev/sdb1 it only shows 2199 GB for size.
> Now, when I connected this drive to the third machine, it works
> perfectly.  My data is still intact, I can see the LUKS header and I can
> mount the file system.

Aha, so this is some broken mapping for large drives.
Then the EFI header could be something left over that
does not matter at all.
> Now that I've narrowed down the issue, how can I resolve it?  Why can't
> these two computers see the entire drive size?
> Both are custom builds, the drive was connected directly via SATA
> Computer #1
> Abit KN8 Motherboard
> BIOS version 6.00 PG
> AMD Athlon(tm) 64 Processor 3200+
> Computer #2
> Asus A8N32-SLI-Deluxe Motherboard
> BIOS version 1303
> AMD Athlon(tm) 64 X2 Dual Core Processor 3800+
> Do you think I need a BIOS update or am I missing something in the OS?

I suspect that a BIOS update is necessary. For older boards that
coul be problematic. There may also be a hardware limitation in 
there somewhere, I am not sure. 

It may be a good idea to use the drives only via USB on the older

However, not a cryptsetup problem, so let us take this off the list.

Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email: arno at wagner.name 
GnuPG:  ID: 1E25338F  FP: 0C30 5782 9D93 F785 E79C  0296 797F 6B50 1E25 338F
One of the painful things about our time is that those who feel certainty 
are stupid, and those with any imagination and understanding are filled 
with doubt and indecision. -- Bertrand Russell 

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