How to upgrade from Debian 10 to Debian 11

Hello everyone! In this guide, I'll show you how to upgrade from Debian 10 to Debian 11.

1. Updating sources.list from Debian 10 to Debian 11

Let's begin by running updates first:

apt update && apt upgrade -y

Now, open the sources.list:

nano /etc/apt/sources.list

Replace every "buster" with "bullseye" & buster/updates with bullseye-security:

deb http://deb.debian.org/debian buster main
deb-src http://deb.debian.org/debian buster main

deb http://security.debian.org/debian-security buster/updates main
deb-src http://security.debian.org/debian-security buster/updates main

This is how the config should look like after adjusting it correctly:

deb http://deb.debian.org/debian bullseye main
deb-src http://deb.debian.org/debian bullseye main

deb http://security.debian.org/debian-security bullseye-security main
deb-src http://security.debian.org/debian-security bullseye-security main

You could also alternatively try to use:

sed -i 's:buster/updates:bullseye-security:' /etc/apt/sources.list
sed -i 's:buster:bullseye:' /etc/apt/sources.list

2. Downloading new packages

Apply updates:

apt update && apt upgrade -y --without-new-pkgs

Upgrade fully:

apt update && apt full-upgrade -y

Reboot system:

reboot now

After reboot, Debian 11 should be installed successfully.