diskLabelCommit fails within a sysinstall script?

[Jeff Gold]

I am attempting to partition a disk non-interactively using
sysinstall, but I don't seem to be getting this right.  I use the
following script on an 80G drive:

  debug=true
  ufs=/6.2-RELEASE
  mediaSetUFS
  disk=ad0
  partition=all
  bootManager=boot
  diskPartitionEditor
  diskPartitionWrite

  ad0s1a=ufs 1048576 /
  ad0s1b=swap 4194304 none
  ad0s1d=ufs 2097152 /tmp
  ad0s1e=ufs 16777216 /usr
  ad0s1f=ufs 0 /var 1
  diskLabelEditor
  diskLabelCommit
  shutdown

This runs without any evident error, but the relevant contents of /dev
change from just ad0 to ad0, ad0s1 and ad0s1c.  The first two make
sense but ad0s1c is the only device I didn't request.  None of the
ones I did seem to appear.  A boot loader does seem to have been
installed but when I select "F1" for FreeBSD it says "Invalid
partition" and complains that there's "No /boot/loader" to be found.
So I guess the first stage got installed but not the next one?

Can anyone explain why this doesn't work?  I skipped the 'c' partition
because that's what sysinstall wants to do when I run it
interactively, but renaming the devices to include the 'c' makes no
difference.  There is still an s1c and nothing else.  Also, I tried
the syntax in the man page (ad0s1-1 instead of ad0s1a) but that --
perversely -- gives me a bunch of errors about being unable to mount
partitions with the other style names.

                                                                    Jeff