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<!-- retain these comments for translator revision tracking -->
<!-- $Id$ -->
<sect3 id="apt-setup">
<title>Configuring apt</title>
<para>
One of the tools used to install packages on a &debian; system is
a program called <command>apt-get</command>, from the
<classname>apt</classname> package<footnote>
<para>
Note that the program which actually installs the packages is called
<command>dpkg</command>. However, this program is more of a low-level
tool. <command>apt-get</command> is a higher-level tool, which will
invoke <command>dpkg</command> 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.
</para>
</footnote>.
Other front-ends for package management, like <command>aptitude</command>
and <command>synaptic</command>, 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, <command>aptitude</command> is now the
recommended utility for package management.
</para><para>
<command>apt</command> must be configured so that it knows from where to
retrieve packages. The results of this configuration are written to the
file <filename>/etc/apt/sources.list</filename>. You can examine and edit
this file to your liking after the installation is complete.
</para><para>
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
<quote>volatile</quote> update service.
</para><para>
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 <quote>contrib</quote> and <quote>non-free</quote>
sections of the archive.
</para>
<sect4 id="apt-setup-mirror">
<title>Using a network mirror</title>
<para>
One question that will be asked in most cases 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.
</para><para>
If you are <emphasis>not</emphasis> 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 <emphasis>not</emphasis>
to select the <literal>desktop</literal> task in the next step of the
installation.
</para><para>
If you are installing from a full CD or using a CD image (not DVD), using a
network mirror is not required, but is still strongly recommended because a
single CD contains only a fairly limited number of packages. The installer
currently does not support using multiple CD or DVD images during the
installation<footnote>
<para>
Adding that option is planned.
</para>
</footnote>. If you have a limited Internet connection it may still be best
to <emphasis>not</emphasis> select a network mirror here, but to finish the
installation using only what's available on the CD and install additional
packages after the installation (i.e. after you have rebooted into the new
system).
</para><para>
If you are installing from a DVD or using a DVD image, the need to use a
network mirror is a lot smaller, but there is still a chance that some
packages that are part of the tasks you select in the next step will not
be included on the first DVD. This is especially true if you are installing
in another language than English: a number of font and localization packages
are known to be on the second DVD. So, if you have a reasonable Internet
connection it is still advisable to use a network mirror.
</para><para>
<!-- This should probably be documented a bit more extensively in
post-install instead. -->
To install additional packages after the installation you have two options:
<orderedlist>
<listitem><para>
if you have additional CD/DVD images available (from same set as the
installation CD/DVD you are using), you can add those to the
<filename>sources.list</filename> using <command>apt-cdrom</command>;
</para></listitem>
<listitem><para>
manually add a mirror to the <filename>sources.list</filename> using an
editor.
</para></listitem>
</orderedlist>
You can then use one of the package management front-ends to select and
install additional packages<footnote>
<para>
It is possible to add both additional CDs or DVDs <emphasis>and</emphasis>
a network mirror in <filename>/etc/apt/sources.list</filename>. Also adding
a network mirror has the advantage that it will make updates of packages in
point releases of the distribution available for installation.
</para>
</footnote>.
</para><para>
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 on the 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 a) the tasks you select in the next step of the installation, b)
which packages are needed for those tasks, and c) which of those packages
are present on the CD/DVD.
</para><para>
Note 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.
</para>
</sect4>
</sect3>
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