APT pinning is a feature which allows administrators to force APT to choose particular versions of packages which may be available in different versions from different repositories. This allows administrators to ensure that packages are not upgraded to versions which may conflict with other packages on the system, or that have not been sufficiently tested for unwelcome changes.
In order to do this, the pins in APT's preferences file must be modified,[2] although graphical front-ends often allow this more simply.
*en.wikipedia.org/wiki/Apt-pinning#APT_pinning
Note: Before you consider 'pinning', you might want to check *wiki.debian.org/htdocs/modern/img/moin-www.png apt-get.org*wiki.debian.org/htdocs/modern/img/moin-www.png backports.org to see if the package you want has been backported to your release. and
Pinning allows you to run certain packages from one version (stable, testing, unstable) without the necessity of upgrading your entire system. However, pulling in packages from "later" distributions are prone to pull in libraries as well, which might have you end up with a system that has the disadvantages of stable (old software), the disadvantages of unstable/testing (security support not as good as stable, bugs) without the advantages of either.
At its most basic level, pinning involves two files, /etc/apt/sources.list and /etc/apt/preferences.
src:
*wiki.debian.org/AptPinning
^^ read the hw2 fully