vnconfig for part of a file

[Brook Milligan <brook%nmsu.edu@localhost>]

I find that vnconfig is really useful for building disk images for embedded or Xen systems.  However, in some cases the image file must contain information (e.g., boot sectors) in addition to the filesystem.     It is, of course, possible to extract portions with dd to a new file, expose that file as a disk via vnconfig, and then reinsert the file back into the original image with dd.  However, it would make much more sense (I believe) to be able to use vnconfig with options to specify the offset and size of the file subset to treat as a disk image.  For example, I'm thinking of something like the following

	vnconfig -c -o 8192 -s 114688 vnd0 bootdisk.img

as a means to create a virtual disk for the subset of the file bootdisk.img that contains only 114688 sectors beginning at sector 8192.  I feel that this would greatly simplify the task of building disk images for a variety of systems.

Does this make sense?  Would this be hard to do?  Does anyone have the knowledge (or bandwidth) to do this?

Cheers,
Brook