What's inside /etc/apt/sources.list

#linux #bash

And also quite possibly inside /etc/apt/sources.list.d/

Upfront, the /etc/apt/source.list is a configuration file for Linux's Advance Packaging Tool, that holds URLs and other information for remote repositories from where software packages and applications are installed.
Same goes with files inside /etc/apt/sources.list.d/.

Basically, when an installation command is executed, eg. apt-get install <package_name> then the Package Management System looks inside /etc/apt/sources.list and /etc/apt/sources.list.d/ for the remote repository link, and searches for the desired application to be downloaded.

" One of the reasons why there are two places for list instead of one, is in order to make sure data are not overwritten/lost during a system update. /etc/apt/source.list may be overwritten in update as this tend to happen with /etc/profile. That is also why custom configurations that generally goes inside /etc/profile file are preferably placed inside /etc/profile.d/ directory. "

A single link inside /etc/apt/sources.list file looks like this:
deb-src http://security.ubuntu.com/ubuntu eoan-security universe

On interpreting individual word:
deb-src