>It would be really nice if there were a way to have the system pick a
> strategy on boot.

> Proposal:  'etcswitch'.  There would be directories /etc/switch/foo, and
> during boot, if 'etcswitch' is enabled, *before* normal config files are
> read, you get a little prompt on /etc/switch/*, letting you pick a
> configuration.  (Before it nukes your old files, it presumably copies them,
> and you might have a few special ones like /etc/switch/previous.)

I just suffered through the evil twin of this problem.

I finally upgraded my main server here from a 486/66 to a P][/350 (factor of 
ten speed improvements are NICE...), and to make a long story short, fumbled
a lot of the reconfiguration issues (I had the Pentium running for a month or
so independantly before the Brain Transplant).  If there was a centralized
notion of what's involved in configuring a system, it would have been a lot
easier to manage the switchover, rather than hitting the obvious details first
and then cleaning up the wreckage as problems surfaced.  Such a concrete
notion of what the configuration *is* would make switching configurations
a lot easier. ;-)

Now, I grant that there are issues that would have complicated my situation:
the peripherals were substantially different (different ethernet, different
disk controllers, different sizes and numbers of hard drives), and there's a
lot of configuration issues I wouldn't expect that any predesigned mechanism
would cover (for example, the old system had INN 1.4, the new has INN 2.1
(or will when I finish rewriting the config files); the old had NCSA httpd,
the new has Apache (or will when... ;-) )).  But there are a lot of little
fiddly files to adjust even in a base configuration and it was a pain having
to chase them all down one at a time.