Upgrade Debian 10 Buster to Debian 11 Bullseye: A Step-by-Step Guide

Upgrade Debian 10 to Debian 11

This step-by-step tutorial is going to show you how to safely upgrade Debian 10 Buster to Debian 11 Bullseye from command line.

On on August 14th, 2021 the Debian project has finally released a stable version of Debian 11 Bullseye after over 2 years of development. It is comes with a lot of new features as most of the software in this version has been updated. Debian 11 will receive support for the next 5 years just like any other Debian stable version.

Let’s now focus on how you can upgrade from Debian 10 Buster to Debian 11 Bullseye. The upgrade process is quite simple and assumes you are running in the root account.

1. Backup Your System

Please make sure to back up your data. The Debian upgrades are normally safe, but there is always a chance something may go wrong. It is crucial that you have your valuable data safely copied to a backup location, so you can restore it if there are any problems or complications.

You can manually copy important files to a different device (second hard disk, USB drive, another computer on the network, etc).

You can also create a full system image of your current Debian installation with a dedicated system imaging software like CloneZilla. If you wish to use any other backup software you are free to do so, just make sure your data are placed in a safety location.

2. Update All Currently Installed Packages

Before you start upgrading from Debian 10 to Debian 11 it’s important to make sure your currently installed Debian 10 system is up to date. Run the following apt commands in the terminal.

apt update
apt upgrade
apt full-upgrade

Now you can clean any leftover packages.

apt --purge autoremove

Then reboot your Debian 10 for the changes made to apply.


3. Check the Currently Installed Version

Now we will start by verifying that we are currently using the latest Debian 10 point release.

The easiest way on how to check what Debian version you are running is to simply read a content of /etc/debian_version file.

cat /etc/debian_version

An alternative way is by use of lsb_release command. You can use it to displays LSB (Linux Standard Base) information about the Linux distribution.

lsb_release -a
Distributor ID:	Debian
Description:	Debian GNU/Linux 10 (buster)
Release:	10
Codename:	buster

4. Replace Debian 10 with Debian 11 Repositories

The Debian software repositories are defined in the /etc/apt/sources.list file and the /etc/apt/sources.list.d/ directory. Before starting the upgrade procedure, you must reconfigure them to point to the Debian 11 Bullseye repositories.

It is a good practice before updating the software repositories to backup the current software source list first.

mkdir ~/apt
cp /etc/apt/sources.list ~/apt
cp -r /etc/apt/sources.list.d/ ~/apt

Now you can proceed and update the current Debian 10 Buster repository to point to Debian 11 Bullseye repositories.

sed -i 's/buster/bullseye/g' /etc/apt/sources.list
sed -i 's/buster/bullseye/g' /etc/apt/sources.list.d/*

The commands shown above will replace the buster keyword with bullseye in software repositories files.

In Debian 11 Bullseye the security suite is now named bullseye-security instead of bullseye/updates. So you need to locate the following debian-security  lines in the  /etc/apt/sources.list file:

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

And replace them with these ones:

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

The final sources.list file should look like below.

cat /etc/apt/sources.list
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

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

5. Perform a Minimal System Upgrade First

At this point, your Debian 10 system is ready for the upgrade. The next step is to update the repository to let the system recognize the newly added repo URLs.

apt update

In some cases, doing the full upgrade directly might remove large numbers of packages that you will want to keep. So the Debian developers recommend two-part upgrade process to avoid the removal of the packages.

  • Part 1: Minimal system upgrade
  • Part 2: Full system upgrade

In the minimal upgrade, you will update and upgrade all the available packages without installing or removing any other packages.

To perform the minimal system upgrade first, run the command shown below.

apt upgrade --without-new-pkgs

Keep an eye on the screen. If the apt-listchanges package is installed, it will show important information about upgraded packages in a pager after downloading the packages.

Press q after reading to exit the pager and continue the upgrade.

Debian 10 to Debian 11 Upgrade

In addition, you will be asked if you want to restart services without asking.

Debian 10 to Debian 11 Upgrade

You will be also asked what do you want to do with a specific configuration file. If you’re not sure what to do, just go with defaults by simply pressing Enter key.

6. Upgrade Debian 10 to Debian 11

Once minimal system upgrade is finished, run the following command to begin full upgrade.

apt full-upgrade

Do not leave the system unattended, because upgrade process requires various inputs during the upgrade.

Once the Debian 11 upgrade process is completed, you can reboot the system.


Log in to the system and check your Debian version.

cat /etc/debian_version

Or as alternative way by using the lsb_release command:

lsb_release -a
Distributor ID:	Debian
Description:	Debian GNU/Linux 11 (bullseye)
Release:	11
Codename:	bullseye

Congratulations! You have successfully upgraded your system from Debian 10 Buster to Debian 11 Bullseye. Your system will now be running Debian 11 Bullseye.

7. Cleaning up Debian 10 Obsolete Packages

It is good idea to clean your newly upgraded Debian 11 Bullseye system by removing old obsolete packages that are now leftover from your successful upgrade and are not needed anymore.

apt --purge autoremove
apt autoclean


In the above tutorial, you learned how to upgrade Debian 10 Buster to Debian 11 Bullseye. Now you can enjoy the latest packages and hardware support that is provided by the latest Debian release.

We have tried to make this tutorial as simple as possible. Thanks for using it.

For additional help or useful information, we recommend you to check the official Debian upgrade documentation.

If this guide has helped you, please consider buying us a coffee.

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Your support and encouragement are greatly appreciated!


    • Hi Rupert,

      Thank you for your remark. This guide has been tested many times and has proven to work flawlessly.

      However a quick check of the official documentation shows that you are correct.

      As a matter of fact, both options work – with and without “/”.

      Anyway, the correction has been added. Thanks.

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