Upgrading debian (old)stable to debian (new)stable

 Debian 11 was released, now we will show you how to upgrade from any Debian to any new Debian! It means you can upgrade any by example future Debian 12 to future Debian 13, or inclusively oldoldstable to next oldstable..

Debian has a easy way to do, just 4 commands (alpine has the most easy upgrade process, take note of), resumed in:

• First up to date: apt update to security changes. 
• Then apt upgrade to prepare system. 
• Finally apt full-upgrade to finish upgrade.

But those commands are only if two prerequisites are in the way:

1. The repository are pointed to "stable" (event using a code name as most experts does)! 
2. The software installed follow the most close Debian policy, so linked programs will not break.

So lest take part of the details on if you have some differences on the requisites and must upgrade!

First: prepare system

You must install lsb-release package, to dynamically determine current and next to install system (mostly in many servers, desktop always has this package).

apt-get install lsb-release

Second upgrade present system

You must chek if package are in sync with fixeds , is not just "upgrade fashion", some package fixed important problems so then must run:

apt-get upgrade

Take in consideration with only will upgrade and fix Debian packages, any other software like own compiled ones will not be addressed and consequently could not be in sync neither linked property.. 

Later change the repository points:

sed -i 's/$(lsb_release -sc)/stable/g' /etc/apt/sources.list

then runs apt-get update

Finally full changed upgrade

Debian must preconfigure migrations on packages. so best one is to first upgrade minimal essential packages:

apt-get upgrade --without-new-pkgs

Now you can complete upgrade the system for sure:

apt-get full-upgrade

Remarks

This are easy.. just like alpine does, (update, changed repo, and then upgrade), Debian already reconfigure almost any services running..

By exampel if you have SSH, WEBSERVER, MAIL etc of most common services, the Debian package system will ask for important changes to do, based on changes made to the system.

Also this will not afffect the software compiled by your own, on the system, some of those are linked and maybe older packages changed sonames in new versions, this of course will rely on breaking changes.. it suppost a linux admin is a minimal programer so windo shit go to cry!