Upgrade Debian 10 Buster to Debian 11 Bullseye
This guide explains how to upgrade your Debian Linux system from Debian 10 (Buster) to Debian 11 (Bullseye) which is now the current stable release as of August 14th, 2021.
These steps can be preformed as an in place upgrade on a live system from either a local terminal or remote SSH session.
Prior to upgrading, make sure the current system is up-to-date.
apt update && apt upgrade
Switch the Debian repositories from Buster to Bullseye by editing the source file.
Replace all instances of buster with bullseye. Then modify the security lines, replacing buster/updates with bullseye-security.
Current source.list should look similar to this:
deb http://deb.debian.org/debian buster main deb-src http://deb.debian.org/debian buster main deb http://deb.debian.org/debian-security/ buster/updates main deb-src http://deb.debian.org/debian-security/ buster/updates main deb http://deb.debian.org/debian buster-updates main deb-src http://deb.debian.org/debian buster-updates main
Modified source.list will look like this once you're done:
deb http://deb.debian.org/debian bullseye main deb-src http://deb.debian.org/debian bullseye main deb http://deb.debian.org/debian-security/ bullseye-security main deb-src http://deb.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
If you also need the contrib and non-free components, add contrib non-free after main on all lines.
Debian is distributed (mirrored) on hundreds of servers worldwide. In our source.list example above we've used a repository within the United States, to speed up downloads you may choose another Debian mirror based on geographic location.
Third-party software that is installed from Personal Package Archives (PPA) will be disabled during the upgrade process. This may not be applicable to your system, so prior to starting, identify PPA by looking for .list files in the /etc/apt/sources.list.d/ directory. If present, you'll need to update these once the system upgrade has finished. Check with the software distributor on how to do this as software channels outside the standard Debian repositories may not support this new release.
Update the package index.
Upgrade the minimal base system.
Upgrade all other packages and dependencies.
Reboot the system.
Verify your release has been upgraded.
Output will be similar to this.
No LSB modules are available. Distributor ID: Debian Description: Debian GNU/Linux 11 (bullseye) Release: 11 Codename: bullseye
Clear out the local repository of retrieved package files and dependencies that are no longer required.