If you want to install some packages from testing without upgrading your whole stable system to testing you can tell apt how to deal with different releases:

1. add testing and/or unstable repos to your sources.list
2. edit apt.conf
3. edit preferences
4. apt-get install […]

Recommended reading:

• http://www.debian.org/doc/manuals/apt-howto/index.en.html
• man 5 apt_preferences

/etc/apt/apt.conf

APT::Default-Release "stable";

/etc/apt/preferences

Package: *
Pin: release a=stable
Pin-Priority: 900

Package: *
Pin: release a=testing
Pin-Priority: 90

What the pin priorities mean: http://www.debian.org/doc/manuals/apt-howto/ch-apt-get.en.html#s-pin

Tools

• apt-cache policy foo
• apt-show-versions

Howto invoke apt-get

• apt-get install foo/testing
• apt-get install foo=1.0-1
• apt-get install –target-release testing foo