Apt/list

this document explains how apt knows what software is available.

when the user runs the command "apt -la", apt will try to list all available software on each known repo srver.

apt will read it's source file, go to each server in the list and retrieve it's /manifest/APT.db file

it adds each entry to one list and when switching to another server adds that server url to this list.

it now opens "less" to allow the user to view this list.