C. The Debian Package Management Utilities

Contents:
Packages
The Package Management Tools
Using dpkg
Using dselect
Using apt-get
Package Contents and Installation Commands

This appendix introduces you to Debian's package management facilities, which help you manage software applications. Suppose, for example, that after installing Linux, you discover you need an application that you omitted; you can find the missing application's package and use the package management facilities to quickly and easily install the application. Similarly, when a new version of an application becomes available, the package management facilities helps you upgrade painlessly, by preserving the application's configuration files. The package management facilities also let you query the status of your system, helping you determine whether important files have been deleted.

C.1 Packages

A Debian package (or more simply, a package or a deb) is a file that contains files necessary to install an application or software unit. Debian packages are generally named using a convention that lets you determine the name of the package, the version of the software, and the release number of the package. Figure C.1 shows how the components of a package name are arranged.

Figure C.1: The structure of a package name

The important virtue of packages is that they contain meta-information; that is, information about their contents. For example, each package contains a list of other packages needed for correct operation. Similarly, each package contains a list of other packages that conflict with its operation. This meta-information greatly simplifies system administration, which otherwise can become quite a challenge. Each package also contains a checksum, that helps protect package users against viruses and other sorts of tampering with package contents.

Debian packages have several important advantages relative to those used by other package management schemes. To learn more about these, see the comparison of package formats authored by Joey Hess, at http://kitenet.net/~joey/pkg-comp/.