Thanks to Matthias Drochner and Bill Studenmund for pointing out that
I had forgotten to update the "number of partitions" in the disklabel,
which is why my addition of partition h was not working properly.

Just for fun, I retried my boot of my original kernel, using sd0g as
the root partition, with sd0h = sd0b (swap).  This time, savecore did
not complain: presumably it checked sd0h for the core dump and found
none.  However, "swapon" still complained, both during boot and upon
later manual invocation, that /dev/sd0b is not configured, and a
manual attempt to "swapon /dev/sd0h" gave the "already in use" error.

Anyway, as I reported yesterday, I built a special kernel with root
and swap devices hard-coded in, and it works fine.

Thanks again to everyone who replied!


Anne.
-- 
Ms. Anne Bennett, Senior Analyst, IITS, Concordia University, Montreal H3G 1M8
anne@alcor.concordia.ca                                        +1 514 848-7606