6.2.5 Tracking a distribution using APT
To track the testing distribution as it changes, make your
/etc/apt/preferences file look like this:
Package: *
Pin: release a=testing
Pin-Priority: 800
Package: *
Pin: release a=stable
Pin-Priority: 600
Note that tracking the testing distribution can have the side
effect of delaying the installation of packages containing security fixes.
Such packages are uploaded to unstable and migrate to
testing only after a delay.
See apt_preferences(5) for more complicated examples which will
allow you, for example, to track testing while installing selected
packages from unstable.
Examples which lock particular packages at particular versions while tracking
other packages as they are released are available in the examples subdirectory as
preferences.testing and preferences.unstable.
If you mix distributions, e.g., testing with stable
or unstable with stable, you will eventually pull in
core packages such as libc6 from testing or
unstable and there is no guarantee that these will not contain
bugs. You have been warned.
Another example, preferences.stable, forces all packages to be
downgraded to stable.
Downgrading from a later release of a package to an earlier
one is not officially supported in Debian. However, you may find that you have
to downgrade a specific package in order to re-install a version of a package
that works when a new version malfunctions. You may find these previous
package files locally in /var/cache/apt/archives/ or remotely at
https://snapshot.debian.net/. See
also
Rescue using dpkg, Section
6.3.3.
Downgrading from a later release of a distribution to an
earlier one is not officially supported either and is very likely to cause
problems. However, this may be worth trying as a last resort if you are
desperate.
