About Backports
Debian Backports provides new packages with new features on supported Debian stable releases.
As a matter of Backports policy, packages in the stable-backports suite are taken from Debian testing; however, in rare cases such as security updates, packages are taken from unstable. Backports Policy permits this exclusively when such packages will be part of the next Debian stable release. In any case, the new packages are recompiled for use on Debian stable. Backports are expected to make use of the versions of libraries available in Debian stable whenever possible; however, when required, the backporting of additional dependencies is permitted.
When a new Debian release is made, the previous stable suite becomes old-stable. While old stable releases may have Long Term Support, old-stable-backports are only made available for a period of one year after a new Debian stable release has been made. For example, Debian Buster was released 6 July 2019 and stretch-backports was retired one year later. Packages in old-stable-backports must track the versions in stable (or stable/updates for security fixes).
Backports cannot be tested as extensively as Debian stable, and are thus supported on a best-effort basis; there is a risk of incompatibilities with other components in Debian stable, so backports should be used with care! That said, Debian Backports Policy does not allow backports of libraries that would break all dependent packages in stable (eg: new Qt 5.x releases), and by virtue of this, Debian Backports are considered generally safe when used as intended on an individual package basis.
The coinstallability of all available backports is not tested, and it is strongly recommended to opt-into the use of specific backported packages on an as-needed basis.
Add Backports to sources.list
deb http://deb.debian.org/debian bullseye-backports main
to sources.list (or add a new file with the ".list" extension to /etc/apt/sources.list.d/).
Run apt update or apt-get update
Installing a Package from Backports
All backports are deactivated by default so that the normal operation
of a stable installation will not be compromised with potentially
disruptive changes (such as incompatible configuration schema).
Release files make this possible, and all backported packages are
pinned to priority 100 via ButAutomaticUpgrades: yes. To install
something from backports run one of:
apt install <package>/bullseye-backports
apt-get install <package>/bullseye-backports
or
apt install -t bullseye-backports <package>
apt-get install -t bullseye-backports <package>
and of course aptitude may also be used:
aptitude install <package>/bullseye-backports
The Old-stable-sloppy Suite
To guarantee a clean upgrade path from one Debian stable release to the next, packages in Backports cannot be newer than the packages destined for the next Debian stable release; this is a matter of Backports Policy. Anyone who is willing to sacrifice the ability to cleanly and smoothly upgrade between stable releases may "get the latest version available" via old-stable-sloppy. Old-stable-sloppy backports are packages from testing that have been rebuilt for old-stable.
Enabling old-stable-sloppy-backports is near identical to stable-backports, with two notable exceptions. First, in sources.list. Rather than using:
deb http://deb.debian.org/debian buster-backports main
use this instead:
deb http://deb.debian.org/debian buster-backports-sloppy main
Second, Packages in backports-sloppy are provided "as-is" and have no official support. Like old-stable-backports, old-stable-backports-sloppy is taken offline one year after a new Debian release has been made.
Subscribe to the Security Announcements Mailing List (highly recommended)
To receive announcements about security updates for Debian Backports, subscribe to the debian-backports-announce mailing list.
Report Bugs
Please report bugs in backported packages to the backports mailing list and NOT to the Debian BTS!