A package in Debian is delivered in a single file using the .deb extension to identify it as a binary package. This package file contains all the data and program executable files delivered by the package, as well as all the control information used by the package manager to install the files correctly on your system. While you can install packages without the tools, it is much easier to install Debian packages with the Debian Package Management Tools.
This chapter covers the three primary package management tools found in the Debian distribution; dpkg, dselect, and apt-get. The following pages will cover the use of these tools to install, upgrade, or remove individual packages as well as groups of packages. In addition the use of these tools to provide administrative information about the packages installed on the system which will be described. Details about how packages are actually built can be found in the developers documents provided with the Debian system, and are not a part of the material covered in this chapter.
dpkg is a command line interface to the basic package management functions in a Debian system. This is the earliest tool provided for the system, and provides all the direct access to the package manager database as well as the direct manipulation of the packages to install, upgrade, or remove individual packages. In this section the use of dpkg to install packages, check on the status of packages, upgrade packages, check which packages are installed on the system correctly and which failed to completely install, and removal of the package will be discussed. Examples of each activity will be provided to make clear how each of these features can be used on your new system.
While dpkg is the real workhorse of the package management system, the system maintainer will probably only use it on rare occasions to actually install packages. The first tool to provide features that allowed the installation of multiple packages in one pass was dselect. This tool is a full screen interface that allows browsing and choosing from all of the packages available in an archives. This section will cover such tasks as selecting an archival method, updating the available packages database, selecting packages for installation, dependency management, installation, and configuration. While this tool has some limitations, there are access methods for every conceivable archives type, and is often the tool of choice for installing several packages at once.
The major deficit for dselect is that it is incapable of installing the packages in a preferred order. Sometimes this leads to packages that will not install on the first pass because some package that it depends upon has not yet been installed. apt-get understands the order requirements of the packages it is going to install, as well as automatically dealing with the dependencies on the packages specified. While apt-get is primarily a command line interface, it has many advantages when installing multiple packages, and works as well over the net as with a local archives. A complete description of how to set up and use apt-get will be presented in the last section of this chapter and will include a discussion of tasks packages as another way to install multiple packages in a useful group.
While you will most likely use apt-get for all your package installation and upgrade needs, a basic understanding of the other tools will help you make the most out of the package management system provided in the Debian distribution. It is the goal of this chapter to provide you with this basic understanding of the package management tools.