Reliable replication of installed packages

[Evan Simpson <evan@4-am.com>]

I'm trying to come up with a reliable process for "replicating" the set 
of installed packages from one Debian installation to another.  I have 
two use-cases:

1. Restoring a system from backup.
2. Maintaining a secondary server.

I currently use a combination of "dpkg --get-selections" and 
"apt-show-versions", since my systems are mixed stable/testing with 
pinned preferences.  This doesn't quite cut it, since I have to handle 
the testing packages by hand, but at least I can find out which packages 
need it.  Also, in one recent attempt to bootstrap from a minimal 
installation, I had to run "dselect" since "apt-get" didn't seem to see 
the effects of "--get-selections".

Thanks,

Evan @ 4-am