[ubuntu-in] Offline update/upgrade - How does it work

[Narendra Diwate]

I have a really slow Internet connection and most often just getting
the package list updated (doing sudo apt-get update) is difficult.
Getting the updated packaged for a dist-upgrade is an altogether
difficult and different matter, but can often be accomplished if the
sudo apt-get update has succeeded, in part because I use debdelta and
also because I can get synaptic to generate a list of files to
download, then use that list to download from another machine with
fast internet.

I have looked at options like aptonCD, aptzip and apt-offline but
could not get any to work.

So this post is for basically 3 things:

1. Can someone explain (or point me to something online) how a
sources.list file (in /etc/apt/) is translated into a list of uri's of
package lists/.diff files and gpg keys to be downloaded and updated in
the /var/lib/apt/lists/ and then to a list of packages that can be
upgraded.

2. Is there a script or something else that works to update/upgrade a
non-networked machine by downloading the necessary packages from
another machine that is not necessarily Linux/deb based.

3. Apt-offline can be an option but I have no idea how to get it to
work on another machine that has internet. The guide available for it
is unfortunately not very helpful as I have no clue about python that
is a requirement.

-- 
Regards

Narendra Diwate