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Diffstat (limited to 'nixos/doc/manual/configuration/customizing-packages.xml')
| -rw-r--r-- | nixos/doc/manual/configuration/customizing-packages.xml | 129 |
1 files changed, 61 insertions, 68 deletions
diff --git a/nixos/doc/manual/configuration/customizing-packages.xml b/nixos/doc/manual/configuration/customizing-packages.xml index 8aa01fb57a095..03b5bb53197bd 100644 --- a/nixos/doc/manual/configuration/customizing-packages.xml +++ b/nixos/doc/manual/configuration/customizing-packages.xml @@ -3,91 +3,84 @@ xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-customising-packages"> + <title>Customising Packages</title> -<title>Customising Packages</title> + <para> + Some packages in Nixpkgs have options to enable or disable optional + functionality or change other aspects of the package. For instance, the + Firefox wrapper package (which provides Firefox with a set of plugins such as + the Adobe Flash player) has an option to enable the Google Talk plugin. It + can be set in <filename>configuration.nix</filename> as follows: <filename> + nixpkgs.config.firefox.enableGoogleTalkPlugin = true; </filename> + </para> -<para>Some packages in Nixpkgs have options to enable or disable -optional functionality or change other aspects of the package. For -instance, the Firefox wrapper package (which provides Firefox with a -set of plugins such as the Adobe Flash player) has an option to enable -the Google Talk plugin. It can be set in -<filename>configuration.nix</filename> as follows: - -<filename> -nixpkgs.config.firefox.enableGoogleTalkPlugin = true; -</filename> -</para> - -<warning><para>Unfortunately, Nixpkgs currently lacks a way to query -available configuration options.</para></warning> - -<para>Apart from high-level options, it’s possible to tweak a package -in almost arbitrary ways, such as changing or disabling dependencies -of a package. For instance, the Emacs package in Nixpkgs by default -has a dependency on GTK+ 2. If you want to build it against GTK+ 3, -you can specify that as follows: + <warning> + <para> + Unfortunately, Nixpkgs currently lacks a way to query available + configuration options. + </para> + </warning> + <para> + Apart from high-level options, it’s possible to tweak a package in almost + arbitrary ways, such as changing or disabling dependencies of a package. For + instance, the Emacs package in Nixpkgs by default has a dependency on GTK+ 2. + If you want to build it against GTK+ 3, you can specify that as follows: <programlisting> -environment.systemPackages = [ (pkgs.emacs.override { gtk = pkgs.gtk3; }) ]; +<xref linkend="opt-environment.systemPackages"/> = [ (pkgs.emacs.override { gtk = pkgs.gtk3; }) ]; </programlisting> + The function <varname>override</varname> performs the call to the Nix + function that produces Emacs, with the original arguments amended by the set + of arguments specified by you. So here the function argument + <varname>gtk</varname> gets the value <literal>pkgs.gtk3</literal>, causing + Emacs to depend on GTK+ 3. (The parentheses are necessary because in Nix, + function application binds more weakly than list construction, so without + them, <xref linkend="opt-environment.systemPackages"/> would be a list with + two elements.) + </para> -The function <varname>override</varname> performs the call to the Nix -function that produces Emacs, with the original arguments amended by -the set of arguments specified by you. So here the function argument -<varname>gtk</varname> gets the value <literal>pkgs.gtk3</literal>, -causing Emacs to depend on GTK+ 3. (The parentheses are necessary -because in Nix, function application binds more weakly than list -construction, so without them, -<literal>environment.systemPackages</literal> would be a list with two -elements.)</para> - -<para>Even greater customisation is possible using the function -<varname>overrideAttrs</varname>. While the -<varname>override</varname> mechanism above overrides the arguments of -a package function, <varname>overrideAttrs</varname> allows -changing the <emphasis>attributes</emphasis> passed to <literal>mkDerivation</literal>. -This permits changing any aspect of the package, such as the source code. -For instance, if you want to override the source code of Emacs, you -can say: - + <para> + Even greater customisation is possible using the function + <varname>overrideAttrs</varname>. While the <varname>override</varname> + mechanism above overrides the arguments of a package function, + <varname>overrideAttrs</varname> allows changing the + <emphasis>attributes</emphasis> passed to <literal>mkDerivation</literal>. + This permits changing any aspect of the package, such as the source code. For + instance, if you want to override the source code of Emacs, you can say: <programlisting> -environment.systemPackages = [ +<xref linkend="opt-environment.systemPackages"/> = [ (pkgs.emacs.overrideAttrs (oldAttrs: { name = "emacs-25.0-pre"; src = /path/to/my/emacs/tree; })) ]; </programlisting> + Here, <varname>overrideAttrs</varname> takes the Nix derivation specified by + <varname>pkgs.emacs</varname> and produces a new derivation in which the + original’s <literal>name</literal> and <literal>src</literal> attribute + have been replaced by the given values by re-calling + <literal>stdenv.mkDerivation</literal>. The original attributes are + accessible via the function argument, which is conventionally named + <varname>oldAttrs</varname>. + </para> -Here, <varname>overrideAttrs</varname> takes the Nix derivation -specified by <varname>pkgs.emacs</varname> and produces a new -derivation in which the original’s <literal>name</literal> and -<literal>src</literal> attribute have been replaced by the given -values by re-calling <literal>stdenv.mkDerivation</literal>. -The original attributes are accessible via the function argument, -which is conventionally named <varname>oldAttrs</varname>.</para> - -<para>The overrides shown above are not global. They do not affect -the original package; other packages in Nixpkgs continue to depend on -the original rather than the customised package. This means that if -another package in your system depends on the original package, you -end up with two instances of the package. If you want to have -everything depend on your customised instance, you can apply a -<emphasis>global</emphasis> override as follows: - + <para> + The overrides shown above are not global. They do not affect the original + package; other packages in Nixpkgs continue to depend on the original rather + than the customised package. This means that if another package in your + system depends on the original package, you end up with two instances of the + package. If you want to have everything depend on your customised instance, + you can apply a <emphasis>global</emphasis> override as follows: <screen> nixpkgs.config.packageOverrides = pkgs: { emacs = pkgs.emacs.override { gtk = pkgs.gtk3; }; }; </screen> - -The effect of this definition is essentially equivalent to modifying -the <literal>emacs</literal> attribute in the Nixpkgs source tree. -Any package in Nixpkgs that depends on <literal>emacs</literal> will -be passed your customised instance. (However, the value -<literal>pkgs.emacs</literal> in -<varname>nixpkgs.config.packageOverrides</varname> refers to the -original rather than overridden instance, to prevent an infinite -recursion.)</para> - + The effect of this definition is essentially equivalent to modifying the + <literal>emacs</literal> attribute in the Nixpkgs source tree. Any package in + Nixpkgs that depends on <literal>emacs</literal> will be passed your + customised instance. (However, the value <literal>pkgs.emacs</literal> in + <varname>nixpkgs.config.packageOverrides</varname> refers to the original + rather than overridden instance, to prevent an infinite recursion.) + </para> </section> |