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1<section xmlns="http://docbook.org/ns/docbook"
2 xmlns:xlink="http://www.w3.org/1999/xlink"
3 xmlns:xi="http://www.w3.org/2001/XInclude"
4 version="5.0"
5 xml:id="sec-declarative-package-mgmt">
6
7<title>Declarative Package Management</title>
8
9<para>With declarative package management, you specify which packages
10you want on your system by setting the option
11<option>environment.systemPackages</option>. For instance, adding the
12following line to <filename>configuration.nix</filename> enables the
13Mozilla Thunderbird email application:
14
15<programlisting>
16environment.systemPackages = [ pkgs.thunderbird ];
17</programlisting>
18
19The effect of this specification is that the Thunderbird package from
20Nixpkgs will be built or downloaded as part of the system when you run
21<command>nixos-rebuild switch</command>.</para>
22
23<para>You can get a list of the available packages as follows:
24<screen>
25$ nix-env -qaP '*' --description
26nixos.firefox firefox-23.0 Mozilla Firefox - the browser, reloaded
27<replaceable>...</replaceable>
28</screen>
29
30The first column in the output is the <emphasis>attribute
31name</emphasis>, such as
32<literal>nixos.thunderbird</literal>. (The
33<literal>nixos</literal> prefix allows distinguishing between
34different channels that you might have.)</para>
35
36<para>To “uninstall” a package, simply remove it from
37<option>environment.systemPackages</option> and run
38<command>nixos-rebuild switch</command>.</para>
39
40<xi:include href="customizing-packages.xml" />
41<xi:include href="adding-custom-packages.xml" />
42
43</section>