What is a Source List (sources.list) Configuring APT

What is Debian Source List?

The Debian source list is a central component of the Debian package management system. This list is used by the Debian package manager (apt) to determine which repositories to retrieve packages from. Every Debian distribution includes some repositories by default, but users can edit this list to add or remove their own repositories.

The source list contains the repositories' URLs, distribution information, and security keys; It is usually located in the [/etc/apt/sources.list] file.

Additional and 3rd party repository definitions can be found in the [/etc/apt/sources.list.d] directory.

For example:

sudo nano /etc/apt/sources.list
sudo nano /etc/apt/sources.list.d
sudo apt update

For instance:

#deb cdrom:[Debian GNU/Linux 12.2.0 _Bookworm_ - Official amd64 DVD Binary-1 with firmware 20231007-10:29]/ bookworm main non-free-firmware

deb http://debian.gnu.gen.tr/debian/ bookworm main contrib non-free non-free-firmware
deb-src http://debian.gnu.gen.tr/debian/ bookworm main contrib non-free non-free-firmware

deb http://security.debian.org/debian-security bookworm-security main contrib non-free non-free-firmware
deb-src http://security.debian.org/debian-security bookworm-security main contrib non-free non-free-firmware

# bookworm-updates, to get updates before a point release is made;
# see https://www.debian.org/doc/manuals/debian-reference/ch02.en.html#_updates_and_backports
deb http://debian.gnu.gen.tr/debian/ bookworm-updates main contrib non-free non-free-firmware
deb-src http://debian.gnu.gen.tr/debian/ bookworm-updates main contrib non-free non-free-firmware

For instance: sources.list.d

cd /etc/apt/sources.list.d/
touch google-chrome.list
nano /etc/apt/sources.list.d/google-chrome.list
#Add File: deb [arch=amd64] http://dl.google.com/linux/chrome/deb/ stable main