d88721e440
This is based on a prototype Nicolas B. Pierron worked on during a discussion we had at FOSDEM. A new version with a workaround for problems of the reverted original. Discussion: https://github.com/NixOS/nixpkgs/commit/3f2566689
76 lines
2.3 KiB
XML
76 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>Modules that are imported can also be disabled. The option
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declarations and config implementation of a disabled module will be
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ignored, allowing another to take it's place. This can be used to
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import a set of modules from another channel while keeping the rest
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of the system on a stable release.</para>
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<para><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
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be disabled. This can either be the full path to the module or a
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string with the filename relative to the modules path
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(eg. <nixpkgs/nixos/modules> for nixos).
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</para>
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<para>This example will replace the existing postgresql module with
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the version defined in the nixos-unstable channel while keeping the
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rest of the modules and packages from the original nixos channel.
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This only overrides the module definition, this won't use postgresql
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from nixos-unstable unless explicitly configured to do so.</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 http://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>This example shows how to define a custom module as a
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replacement for an existing module. Importing this module will
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disable the original module without having to know it's
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implementation details.</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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