Upgrading Debian 10 (buster) to Debian 11 (bullseye)

Debian 11 is codenamed “bullseye”. Release date 15.08.2021.

Major changes:

– Linux kernel updated to version 5.10 (kernel 4.19 was shipped in Debian 10);

– Updated server applications, including Apache httpd 2.4.48, BIND 9.16, Dovecot 2.3.13, Exim 4.94, Postfix 3.5, MariaDB 10.5, nginx 1.18, PostgreSQL 13, Samba 4.13, OpenSSH 8.4;

– Updated server applications, including Apache httpd 2.4.48, BIND 9.16, Dovecot 2.3.13, Exim 4.94, Postfix 3.5, MariaDB 10.5, nginx 1.18, PostgreSQL 13, Samba 4.13, OpenSSH 8.4;

– Changed format of lines in /etc/apt/sources.list file related to security issues. The {dist} -updates lines have been renamed to {dist} -security. In sources.list, it is allowed to separate the blocks “[]»Several spaces;

First, let’s update the current system.

$ sudo apt update 
$ sudo apt upgrade -y
$ sudo apt autoremove -y
$ sudo apt dist-upgrade -y

Change the buster repository to bullseye

$ sudo nano /etc/apt/sources.list
### Debian 11 (bullseye)
deb https://deb.debian.org/debian bullseye main contrib non-free
deb-src https://deb.debian.org/debian bullseye main contrib non-free

deb https://deb.debian.org/debian-security/ bullseye-security main contrib non-free
deb-src https://deb.debian.org/debian-security/ bullseye-security main contrib non-free

deb https://deb.debian.org/debian bullseye-updates main contrib non-free
deb-src https://deb.debian.org/debian bullseye-updates main contrib non-free

If other repositories are connected to the system, do not forget to change them too.

Updating the list of available packages for the new release

$ sudo apt update

We will update the system in 2 stages.

Minimal update first

$ sudo apt upgrade -y

After completing the minimal update, run the full

$ sudo apt dist-upgrade -y

Reboot

$ sudo reboot

We clean the trash

$ sudo apt autoremove -y

Checking the OS version

$ cat /etc/*release