I'm trying to figure out a reasonably simple and reliable 
backup strategy for my NetBSD 1.5.2 system.  The machine now 
lives at a co-lo facility, and is running as a web and mail 
server, with a bunch of other apps installed.  Some software 
has been installed using pkgsrc, and some built directly. I'm 
manually backing up web content, mail folders, etc., but if I 
had a catastrophic system failure, it would take days to get 
all of the apps back in place.

I've built another machine with very similar (but not identical)
hardware, for use as a backup server.  I'd like to duplicate as
much as possible from the "live" server onto this machine, so I
don't have to reinvent the wheel, installing and configuring a
dozen different apps.  The best possible solution would be to have 
the backup machine alive and running as a secondary server, with 
all content and new apps automagically transferred from the primary 
and DNS sharing the load between the systems.  At a minimum, I'd 
like to be able to move the backup machine to the co-lo facility, 
change its IP address, and have it come up and run with minimal 
impact on operations.

The bottom line is, how do I do this as simply as possible, and
without creating a huge security compromise?  Is rsync the right
approach, or is there something better?

Thanks in advance for any good advice!

- Dave Melton