pkg database backup and restore

[DW]

Hello,

Can anyone provide some practical insight into best methods of backing 
up and restoring package databases?

Inside of /var/db there are 2 directories:
    /var/db/ports
    and
    /var/db/pkg

/var/db/ports I pretty much understand; that seems to simply be the 
config options saved from when a port is installed. ok.


/var/db/pkg contains:

    pkgdb.db
   
    and a subdirectory for every port installed.


If part of a normal backup routine, we are regularly backing up 
/var/db/pkg, how can we best use that backup in a scenario in which a 
machine needs to be rebuilt from scratch, and we're trying to save time 
going through and doing a portinstall on everything we can remember that 
should be installed? (or alternatively taking a backup of the results 
from a periodic "pkg_info > installed_packages.txt" and painstakenly 
going through the list and reinstalling everything one-by-one).

Essentially, we're just looking for a streamlined approach to restoring 
the installed ports when we need to rebuild a machine.


Thanks,
DW