nixpkgs/doc/packageconfig.xml

<chapter xmlns="http://docbook.org/ns/docbook"
         xmlns:xlink="http://www.w3.org/1999/xlink"
         xml:id="chap-packageconfig">

<title>nixpkgs global configuration</title>

    <para>
        Nix packages can be configured to allow or deny certain
        options.
    </para>

    <para>
        To apply the configuration edit <filename>~/.nixpkgs/config.nix</filename>
        and set it like
        <programlisting>
            {
                allowUnfree = true;
            }
        </programlisting>
        and will allow the Nix package manager to install unfree licensed packages.

        The configuration as listed also applies to NixOS under <option>nixpkgs.config</option> set.
    </para>

    <itemizedlist>
        <listitem>
            <para>
                Allow installing of packages that are distributed under unfree license by setting
                <programlisting>
                  allowUnfree = true;
                </programlisting>
                or deny them by setting it to <literal>false</literal>.
            </para>
            <para>
                Same can be achieved by setting the environment variable:
                <programlisting>
                    export NIXPKGS_ALLOW_UNFREE=1
                </programlisting>
            </para>
        </listitem>

        <listitem>
            <para>
                Whenever unfree packages are not allowed, single packages can
                still be allowed by a predicate function that accepts package
                as an argument and should return a boolean:
                <programlisting>
                  allowUnfreePredicate = (pkg: ...);
                </programlisting>

                Example to allow flash player only:
                <programlisting>
                  allowUnfreePredicate = (pkg: pkgs.lib.hasPrefix "flashplayer-" pkg.name);
                </programlisting>
            </para>
        </listitem>

        <listitem>
            <para>
                Whenever unfree packages are not allowed, packages can still be
                whitelisted by their license:
                <programlisting>
                  whitelistedLicenses = with stdenv.lib.licenses; [ amd wtfpl ];
                </programlisting>
            </para>
        </listitem>

        <listitem>
            <para>
                In addition to whitelisting licenses which are denied by the
                <literal>allowUnfree</literal> setting, you can also explicitely
                deny installation of packages which have a certain license:
                <programlisting>
                  blacklistedLicenses = with stdenv.lib.licenses; [ agpl3 gpl3 ];
                </programlisting>
            </para>
        </listitem>
    </itemizedlist>

    <para>
        A complete list of licenses can be found in the file
        <filename>lib/licenses.nix</filename> of the nix package tree.
    </para>

</chapter>