Date: Fri, 3 Jun 2005 12:00:50 -0700 (PDT)
From: Jeremy Cooper <jeremy at baymoo dot org>
To: mk at neon1 dot net
Subject: miniBSD additions

Hi there.  I'm sorry I don't know your name, but you are listed at the
author of the document "miniBSD - reducing FreeBSD", which I found at

https://neon1.net/misc/minibsd.html

I bought a Soekris net4521 on Sunday and it arrived today.  I found your
webpage and tried using it to make a usable FreeBSD on my 128MB flash
card.  There is a fatal flaw in your otherwise very nice page!  The flaw
is that, using your instructions, you end up with a non-bootable CF card
due to differences between bsdlabel and the 4521's opinion of the CF card
geometry.

I found that I had to do the following:

1) Stick the desired flash card into the Soekris and power it up.  Look
for the BIOS information line that reads:

  Pri Mas <flash- manufacturer-name> LBA xxx-yyy-zzz

This line tells you how the Soekris interprets the CF card.

  xxx - Number of cylinders
  yyy - Number of heads
  zzz = Number of sectors per track

2) Ammend your instructions under section 11 "Generating the flash image".
You need to add instructions on how to set the geometry of the image.

--- FreeBSD 5.x ---

FreeBSD 5 allows you to fake the geometry of a vn device at the time
you run mdconfig.  To do this, modify your  current text as follows:


  Let's use this disk image file as a vn device so we can disklabel it:

  FreeBSD 4.7:
   ...
  FreeBSD 5.x:
  mdconfig -a -t vnode -u 0 -f /usr/minibsd-disk.bin -x <sec/trk> -y <heads>

(Notice the addition of the -x and -y arguments.)

Once you have accomplished this step in FreeBSD 5.x, you are all set.
The remaining instructions (bsdlabel) will query the kernel for
the geometry automatically.

---  FreeBSD 4.x ---

FreeBSD 4.7 doesn't have the ability to set the image geometry
at vnconfig time.  Instead, you have to inform the kernel of the
geometry using the fdisk utility.

You begin by creating a small configuration file for fdisk.  This
configuration file contains three commands.  The first command sets the
image's geometry.  The second command creates a BIOS partition that
spans the entire drive, and the last command makes the partition active and
bootable.  The configuration file is a text file with one command per
line:

  g c<cylinders> h<heads> s<sectors-per-track>
  p 1 <sectors-per-track> <total-sectors MINUS sectors-per-track>
  a 1

In my case, my flash card has 250880 sectors and the Soekris interprets
its geometry as having 980 cylinders, 8 heads, and 32 sectors per
track.  Thus, my configuration file read:

  g c980 h8 s32
  p 1 32 250848
  a 1

With the configuration file in place, you are ready to run fdisk to set
the geometry:

  fdisk -f minibsd-disk.config vn0

Then you can continue at the "disklabel -Brw vn0 auto" step.


Thanks for the web page.  It helped a lot!
-Jeremy