what to do when libc6 upgrade goes bad

[Dan <dhugo@reallycool.com>]

Greetings--

I just made an attempt at upgrading my installed libc6 using
libc6_2.0.7.19981211-6.deb.  I have a 2.0 complete install, but I was
going to try GnuCash, which requires guile 1.3, which requires a few
things that are newer than Deb2.0.

Anyway, it didn't go so well, apparently, since some of the other libs
that guile depends on didn't install due to errors, along the lines of
"unable to link" or somesuch (I am embarrassed to say I did not write
the message down, as I was rather frantic in short order).

Having updated libc6, I didn't know whether a reboot was in order, since
that is a fairly important library for just about everything.  Well,
this was a bad idea, since my machine hung rebooting, and then nothing
would run once the kernel finished starting.  Couldn't log in, rescue
disk doesn't have dpkg, and I was sorta stuck, and sort of frantic
(moreso, in fact).

So I just reinstalled and reconfigured the base package using the debian
installer, which turned out to be sort of okay... it had the desired
effect of replacing libc6 with an older version, and it left almost
everything else intact. (Actually, smail won't run anymore... it just
bails on startup, despite the fact that the config files seem to be
there... any thoughts?)

The question, then, is what to do NEXT TIME I do something dumb like
this... how can I avoid getting stuck in this situation, given that I
have a 2.0 CD... 

Any suggestions appreciated, regarding the best way to backtrack when
libc6 upgrades go bad, or how to get smail to run again.

Thanks
Dan Hugo