Re: cryptsetup on a loopback device with an offset fails

[Sam Lowry <lowry@altern.org>]

I subbmitted the question to the upstream developers and they say
that --offset is not supported in luksFormat mode anyway.

The correct way would be either to use kpartx

  losetup /dev/loop0 lenny.img
  kpartx -a /dev/loop0
  cryptsetup luksFormat /dev/mapper/loop0p2 (for 2nd partition)

or to set up the loop device itself with an offset

  losetup -o 98703360 /dev/loop0 lenny.img
  cryptsetup luksFormat /dev/loop0

On Mon, Jul 06, 2009 at 10:32:31PM +0200, Michel Messerschmidt wrote:
> On Mon, Jul 06, 2009 at 10:51:44AM +0200, Sam Lowry wrote:
> >   losetup /dev/loop0 lenny.img
> >   mkdir lenny
> >   mount lenny.img lenny -t ext3 -o loop=/dev/loop0,offset=98703360
> 
> losetup offset is in bytes (see 'man losetup')
> 
> >   cryptsetup luksFormat --offset=98703360 /dev/loop0
> >   >Command failed: Failed to write to key storage
> 
> cryptsetup offset is in sectors (see 'cryptsetup --help')
> 
> 
> HTH,
> Michel
>