9.1 upgrade fails: Shared object"libc.so.12" not found

[Bob Bernstein <poobah%ruptured-duck.com@localhost>]

The message shown is what appeared as I finished what appeared 
to be an uneventful upgrade from an old 'current' netbsd (May 
of last year) to amd64 9.1.

That message, about a missing libc.so.12, was interspersed on 
the upgrade screen reporting almost complete success in checking 
/etc. There was mention of one failed test: gid. (I did not 
investigate it.)

After the line:
kern.module.path=/stand/amd64/9.1/modules

trouble appeared:
panic init died (signal 0, exit 1)
cpu0 begin traceback...
vpanic() at netbsd:vpanic+0x160

...and so on.

I looked in the NetBSD wiki for a gdb-for-Dummies. I don't even 
know how to gather more evidence from the screen showing the 
crash, but I could transcribe more lines and append them to the 
few I show above if it would be useful.

Any suggestions would be most welcome. I have only used gdb 
under fairly close supervision, which I am, of course, willing 
to do again!

Thank you.

--
RSB