[dm-crypt] backup of luks header example in the FAQ has a wrong path

Arno Wagner arno at wagner.name
Sun Jan 15 00:01:13 CET 2012


On Sat, Jan 14, 2012 at 05:32:27PM -0500, .. ink .. wrote:
> using cryptsetup 1.4.1
> At the section on how to backup a luks header, the example given is below:
> cryptsetup luksHeaderBackup --header-backup-file h /dev/mapper/c1
> The usage of "/dev/mapper" path implies running the command on the mapper,
> when i do that i get the following output:
> [root at mtz build]# cryptsetup luksOpen /dev/sdc1 abc
> Enter passphrase for /dev/sdc1:
> [root at mtz build]# cryptsetup luksHeaderBackup --header-backup-file
> backup.img  /dev/mapper/abc ; echo $?
> Device /dev/mapper/abc is not a valid LUKS device.
> 1
> The command errors out when using the mapper address as FAQ suggests.
> When i use the device directly, it works as shown below:
> [root at mtz build]# cryptsetup luksHeaderBackup --header-backup-file
> backup.img  /dev/sdc1 ; echo $?
> 0
> It looks like the command to backup the header is supposed to be run on the
> device its self and not on the mapper as the FAQ suggests.

Ah, yes. Well spotted. I think I was confused because I usually test 
LUKS on loop-files. Fixed in SVN and Wiki.

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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