70 lines
2.2 KiB
Markdown
70 lines
2.2 KiB
Markdown
# Replace Modules {#sec-replace-modules}
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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
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ignored, allowing another to take its place. This can be used to
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import a set of modules from another channel while keeping the rest of
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the system on a stable release.
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`disabledModules` is a top level attribute like `imports`, `options` and
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`config`. It contains a list of modules that will be disabled. This can
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either be:
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- the full path to the module,
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- or a string with the filename relative to the modules path (eg. \<nixpkgs/nixos/modules> for nixos),
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- or an attribute set containing a specific `key` attribute.
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The latter allows some modules to be disabled, despite them being distributed
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via attributes instead of file paths. The `key` should be globally unique, so
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it is recommended to include a file path in it, or rely on a framework to do it
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for you.
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This example will replace the existing postgresql module with the
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version defined in the nixos-unstable channel while keeping the rest of
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the modules and packages from the original nixos channel. This only
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overrides the module definition, this won't use postgresql from
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nixos-unstable unless explicitly configured to do so.
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```nix
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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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```
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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 its implementation details.
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```nix
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{ config, lib, pkgs, ... }:
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let
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inherit (lib) mkIf mkOption types;
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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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```
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