live build on isolated com or net

["jan.weber@pcr.cz" <jan.weber@pcr.cz>]

I appreciate your work, but
- I do my experiments in fully isolated forensic network (no connect to Internet even ftp.debian.org)
- I prepare and study live-build my at my weekend cottage (no connect to Internet even ftp.debian.org)
- in both cases I use local debian mirror - usually outdated, hence
using 'deb [trusted=yes] http://....' and 'Acquire { Check-Valid-Until "false" ; };' 

First I wrote this e-mail, I googled the net if is there some general config, 
then I made some experiments with /etc/hosts and local dns, 
but with no final luck. 
Perhaps there is (or could be) some general setting for the main TRUSTED debian mirror.

As I feel it, the live-build create a separate chroot folder, which is finally converted into an image. 
My question is why? while there is a fully functional debian system (installed by myself) 
which I want to convert into a live image. I know, that I can (hopefully) use the package list 
from existing system for the live build, but then why not to automate such process?

Thanks 
Jan

P.S.
please eventually: 
Reply-To: <jan.weber@volny.cz>