Debian is a free operating system (OS) for your computer. An operating system is the set of basic programs and utilities that make your computer run.
Debian provides more than a pure OS: it comes with over 51000 packages, precompiled software bundled up in a nice format for easy installation on your machine.
You might be in a situation where you have a system with an old Debian version that has reached end of life, like wheezy, etc., and a distribution upgrade is not an option for you (maybe because you have customized the system so much that you fear breaking the system by doing a distribution upgrade). The “normal” repositories for these old versions do not exist anymore, which means you cannot install new software or update existing packages using apt. This tutorial shows how you can modify your /etc/apt/sources.list to still get packages for your old Debian version using apt.
I do not issue any guarantee that this will work for you!
Step 1: Configure /etc/apt/sources.list
After a Debian version has reached EOL (end of life), its repositories go to the Debian archive. Therefore we can use this archive to get packages for our distribution. The syntax for our /etc/apt/sources.list is as follows:
deb http://archive.debian.org/debian/ <version> main non-free contrib deb-src http://archive.debian.org/debian/ <version> main non-free contrib
Step 2: Install debian-archive-keyring package
apt-get update apt-get install debian-archive-keyring
Step 3: Update your package lists
apt-get update apt-get upgrade