One of the tools used to install packages on a &debian; system is a program called apt-get, from the apt package Note that the program which actually installs the packages is called dpkg. However, this program is more of a low-level tool. apt-get is a higher-level tool, which will invoke dpkg as appropriate. It knows how to retrieve packages from your CD, the network, or wherever. It is also able to automatically install other packages which are required to make the package you're trying to install work correctly. . Other front-ends for package management, like aptitude and synaptic, are also in use. These front-ends are recommended for new users, since they integrate some additional features (package searching and status checks) in a nice user interface. In fact, aptitude is now the recommended utility for package management. apt must be configured so that it knows from where to retrieve packages. The results of this configuration are written to the file /etc/apt/sources.list. You can examine and edit this file to your liking after the installation is complete. If you are installing at default priority, the installer will largely take care of the configuration automatically, based on the installation method you are using and possibly using choices made earlier in the installation. In most cases the installer will automatically add a security mirror and, if you are installing the stable distribution, a mirror for the volatile update service. If you are installing at a lower priority (e.g. in expert mode), you will be able to make more decisions yourself. You can choose whether or not to use the security and/or volatile update services, and you can choose to add packages from the contrib and non-free sections of the archive. If you are installing from a CD or a DVD that is part of a larger set, the installer will ask if you want to scan additional CDs or DVDs. If you have additional CDs or DVDs available, you probably want to do this so the installer can use the packages included on them. If you do not have any additional CDs or DVDs, that is no problem: using them is not required. If you also do not use a network mirror (as explained in the next section), it can mean that not all packages belonging to the tasks you select in the next step of the installation can be installed. Packages are included on CDs (and DVDs) in the order of their popularity. This means that for most uses only the first CDs in a set are needed and that only very few people actually use any of the packages included on the last CDs in a set. It also means that buying or downloading and burning a full CD set is just a waste of money as you'll never use most of them. In most cases you are better off getting only the first 3 to 8 CDs and installing any additional packages you may need from the Internet by using a mirror. The same goes for DVD sets: the first DVD, or maybe the first two DVDs will cover most needs. A good rule of thumb is that for a regular desktop installation (using the GNOME desktop environment) only the first three CDs are needed. For the alternative desktop environments (KDE or Xfce), additional CDs are needed. The first DVD easily covers all three desktop environments. If you do scan multiple CDs or DVDs, the installer will prompt you to exchange them when it needs packages from another CD/DVD than the one currently in the drive. Note that only CDs or DVDs that belong to the same set should be scanned. The order in which they are scanned does not really matter, but scanning them in ascending order will reduce the chance of mistakes. One question that will be asked during most installs is whether or not to use a network mirror as a source for packages. In most cases the default answer should be fine, but there are some exceptions. If you are not installing from a full CD or DVD or using a full CD/DVD image, you really should use a network mirror as otherwise you will end up with only a very minimal system. However, if you have a limited Internet connection it is best not to select the desktop task in the next step of the installation. If you are installing from a single full CD or using a full CD image, using a network mirror is not required, but is still strongly recommended because a single CD contains only a fairly limited number of packages. If you have a limited Internet connection it may still be best to not select a network mirror here, but to finish the installation using only what's available on the CD and selectively install additional packages after the installation (i.e. after you have rebooted into the new system). If you are installing from a DVD or using a DVD image, any packages needed during the installation should be present on the first DVD. The same is true if you have scanned multiple CDs as explained in the previous section. Use of a network mirror is optional. One advantage of adding a network mirror is that updates that have occurred since the CD/DVD set was created and have been included in a point release, will become available for installation, thus extending the life of your CD/DVD set without compromising the security or stability of the installed system. In summary: selecting a network mirror is generally a good idea, except if you do not have a good Internet connection. If the current version of a package is available from CD/DVD, the installer will always use that. The amount of data that will be downloaded if you do select a mirror thus depends on the tasks you select in the next step of the installation, which packages are needed for those tasks, which of those packages are present on the CDs or DVDs you have scanned, and whether any updated versions of packages included on the CDs or DVDs are available from a mirror (either a regular package mirror, or a mirror for security or volatile updates). Note that the last point means that, even if you choose not to use a network mirror, some packages may still be downloaded from the Internet if there is a security or volatile update available for them and those services have been configured.