Re: mknbi-dos problem

[Gero Kuhlmann <gero@gkminix.han.de>]

Hello,

Heinrich Rebehn <rebehn@comm.uni-bremen.de> wrote:
> i want to netboot a 4.7 MB dos bootimage containing dos and several
> apps.
> When i try to create the image i get error:
> [...]
> Although i specified a size of 5000 blocks, mknbi-dos is only creating a
> 1440 kB image.
> Why?

mknbi-dos works with two passes:

  1.) generate a source image:
	a) when using an MS-DOS floppy simply use it's image
	b) when using a UNIX directory generate an image which contains
	   a FAT filesystem and put all files from the UNIX directory
	   into this image

  2.) generate the ramdisk image with the specified size (5000 blocks in
      your case) and make the source image fit into the ramdisk by adjusting
      the FAT size. Then copy the contents of the source image without any
      further changes into the ramdisk image.

While step 2 works with any arbitrary ramdisk size as it simply requires
some size adjustments in the FAT, step 1b is a bit more complicated. Step
1b can presently only generate a source image with the standard floppy
sizes. For anything different mknbi-dos would have to compute parameters
like FAT size, cluster size etc. from the amount of data in the UNIX
directory. This is what the DOS format command does when formatting a
new hard disk partition. It's not implemented in the current version
of netboot. Even though you can make the ramdisk as large as you have
memory available in your client, the source image has to fit into a
maximum of 1.44MB. If someone feels encouraged to write the code to
correctly format an arbitrary sized source image please let me know
before you start coding - help is welcome.

gero.

-- 
I'm growing older, but not up.
  - Jimmy Buffett
--
Gero Kuhlmann, Hannover     0511/6497525 (Voice)        gero@gkminix.han.de