79 lines
2.3 KiB
XML
79 lines
2.3 KiB
XML
<section xmlns="http://docbook.org/ns/docbook"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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xmlns:xi="http://www.w3.org/2001/XInclude"
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version="5.0"
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xml:id="sec-replace-modules">
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<title>Replace Modules</title>
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<para>
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Modules that are imported can also be disabled. The option declarations,
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config implementation and the imports of a disabled module will be ignored, allowing another
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to take it's place. This can be used to import a set of modules from another
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channel while keeping the rest of the system on a stable release.
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</para>
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<para>
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<literal>disabledModules</literal> is a top level attribute like
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<literal>imports</literal>, <literal>options</literal> and
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<literal>config</literal>. It contains a list of modules that will be
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disabled. This can either be the full path to the module or a string with the
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filename relative to the modules path (eg. <nixpkgs/nixos/modules> for
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nixos).
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</para>
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<para>
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This example will replace the existing postgresql module with the version
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defined in the nixos-unstable channel while keeping the rest of the modules
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and packages from the original nixos channel. This only overrides the module
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definition, this won't use postgresql from nixos-unstable unless explicitly
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configured to do so.
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</para>
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<programlisting>
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{ config, lib, pkgs, ... }:
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{
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disabledModules = [ "services/databases/postgresql.nix" ];
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imports =
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[ # Use postgresql service from nixos-unstable channel.
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# sudo nix-channel --add https://nixos.org/channels/nixos-unstable nixos-unstable
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<nixos-unstable/nixos/modules/services/databases/postgresql.nix>
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];
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services.postgresql.enable = true;
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}
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</programlisting>
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<para>
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This example shows how to define a custom module as a replacement for an
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existing module. Importing this module will disable the original module
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without having to know it's implementation details.
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</para>
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<programlisting>
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{ config, lib, pkgs, ... }:
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with lib;
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let
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cfg = config.programs.man;
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in
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{
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disabledModules = [ "services/programs/man.nix" ];
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options = {
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programs.man.enable = mkOption {
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type = types.bool;
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default = true;
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description = "Whether to enable manual pages.";
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};
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};
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config = mkIf cfg.enabled {
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warnings = [ "disabled manpages for production deployments." ];
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};
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}
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</programlisting>
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</section>
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