Re: understanding dmsetup

[Anders Ingemann <anders@ingemann.de>]

On 17 August 2013 17:47, Anders Ingemann <anders@ingemann.de> wrote:

So right now I am trying to install grub the proper way on a loop device.
To that end I am following this guide: http://ebroder.net/2009/08/04/installing-grub-onto-a-disk-image/
I understand pretty much everything with the exception of the last '0' in the table info that is passed to `dmsetup create hda'.
As far as I can see the table consists of the following:
echo '0 20971520 linear 7:0 0' | sudo dmsetup create hda
      |    |       |    | | |
      |    |       |    | | +--- ???
      |    |       |    | +--- minor device number
      |    |       |    +--- major device number
      |    |       +--- target type
      |    +--- num sectors
      +---start sector

What does the last '0' do?!

Anders

Ah, I figured it out myself. It's the "start sector". The first '0' is the "logical" start sector.

That answer poses another question, what the hell is the difference between the "logical start sector" and the "start sector"?

The latter seems to be somehow associated with the linear target_type.