7.5 Why doesn't get `foo-data' removed when I uninstall `foo'? How do I make sure old unused library-packages get purged?

Some packages that are split in program (`foo') and data (`foo-data'). This is true for many games, multimedia applications and dictionaries in Debian and has been introduced since some users might want to access the raw data without installing the program or because the program can be run without the data itself, making it optional.

Similar situations occur when dealing with libraries: generally these get installed since packages containing applications depend on them. When the application-package is purged, the library-package might stay on the system. Or: when the application-package no longer depends upon e.g. libdb4.2, but upon libdb4.3, the libdb4.2 package might stay when the application-package is upgraded.

In these cases, `foo-data' doesn't depend on `foo', so when you remove the `foo' package it will not get automatically removed by most package management tools. The same holds true for the library packages. This is necessary to avoid circular dependencies. If you use aptitude (see aptitude, Section 7.1.3) as your package management tool it will, however, track automatically installed packages and remove them when no packages remain that need them in your system.