How to Upgrade from Debian 10 to Debian 11

For those wishing to upgrade from Debian 10 Buster to Debian 11 Bullseye, the process is very simple but does take a while depending on the connection speed to the Internet. An upgrade the other day took about an hour due to slow download speeds from the Debian US repository, likely because a lot of people are upgrading at the moment.

The first step before the upgrade is to back up any important data! While this is often unnecessary, the one time that a backup isn’t made, something will fail and break the system. If a backup/tar file can be made, it is strongly recommended before continuing.

Disclaimers out of the way, let’s begin the upgrade process. Personally, recommend that the current system be completely updated before attempting a distribution upgrade but this is likely unnecessary.

Updating Debian 10 Linux

To completely update the system issue the following command as root or with the ‘sudo‘ utility:

# apt update
# apt upgrade
# apt full-upgrade
# apt --purge autoremove
OR
$ sudo apt update
$ sudo apt upgrade
$ sudo apt full-upgrade
$ sudo apt --purge autoremove

Once updates finish, you need to reboot the system to apply the kernel and other updates:

$ sudo systemctl reboot

Configure APT Sources List

Now it is time to do is prepare the system to look at the new repositories for ‘Bullseye‘. Assuming a standard /etc/apt/sources.list file.

First, make sure to backup sources.list file and then do changes as shown.

$ sudo cp -v /etc/apt/sources.list /root/
$ sudo nano /etc/apt/sources.list

Original /etc/apt/sources.list

Now replace the original ‘Buster‘ lines with the following lines in the /etc/apt/sources.list file to ‘Bullseye‘ as seen in the below screenshot.

deb http://mirrors.linode.com/debian bullseye main
deb-src http://mirrors.linode.com/debian bullseye main
 
deb http://mirrors.linode.com/debian-security bullseye-security/updates main
deb-src http://mirrors.linode.com/debian-security bullseye-security/updates main
 
# bullseye-updates, previously known as 'volatile'
deb http://mirrors.linode.com/debian bullseye-updates main
deb-src http://mirrors.linode.com/debian bullseye-updates main

Newly modified /etc/apt/sources.list file.

Upgrading to Debian 11 from Debian 10

The next step now is to refresh the list of packages available for installation.

$ sudo apt update

Once the utilities have updated the list of packages, it is time to start the upgrade from Debian 10 to Debian 11 process.

$ sudo apt full-upgrade

The Internet connection speed will play a large role in the upgrade as the upgrade will require about a Gigabyte or more of new packages to be downloaded.

Depending on the system’s configuration and installed packages there may be some prompts that require user intervention. The installer will allow the services to be restarted as needed if the user chooses.

As with the fresh Debian 11 install, it is suggested that the user let the system run the upgrade and periodically check in on it as this process will take some time. When it finishes, simply reboot the machine and enjoy Debian 11 in all of its wonder!.

$ sudo systemctl reboot

After reboot, make sure to verify the upgrade.

$ uname -r
$ lsb_release -a

That’s all! We have successfully upgraded to Debian 11 Bullseye from Debian 10 Buster.