pyrox.dev
1# Replace Modules {#sec-replace-modules}
2
3Modules that are imported can also be disabled. The option declarations,
4config implementation and the imports of a disabled module will be
5ignored, allowing another to take its place. This can be used to
6import a set of modules from another channel while keeping the rest of
7the system on a stable release.
8
9`disabledModules` is a top level attribute like `imports`, `options` and
10`config`. It contains a list of modules that will be disabled. This can
11either be:
12 - the full path to the module,
13 - or a string with the filename relative to the modules path (eg. \<nixpkgs/nixos/modules> for nixos),
14 - or an attribute set containing a specific `key` attribute.
15
16The latter allows some modules to be disabled, despite them being distributed
17via attributes instead of file paths. The `key` should be globally unique, so
18it is recommended to include a file path in it, or rely on a framework to do it
19for you.
20
21This example will replace the existing postgresql module with the
22version defined in the nixos-unstable channel while keeping the rest of
23the modules and packages from the original nixos channel. This only
24overrides the module definition, this won't use postgresql from
25nixos-unstable unless explicitly configured to do so.
26
27```nix
28{ config, lib, pkgs, ... }:
29
30{
31 disabledModules = [ "services/databases/postgresql.nix" ];
32
33 imports =
34 [ # Use postgresql service from nixos-unstable channel.
35 # sudo nix-channel --add https://nixos.org/channels/nixos-unstable nixos-unstable
36 <nixos-unstable/nixos/modules/services/databases/postgresql.nix>
37 ];
38
39 services.postgresql.enable = true;
40}
41```
42
43This example shows how to define a custom module as a replacement for an
44existing module. Importing this module will disable the original module
45without having to know its implementation details.
46
47```nix
48{ config, lib, pkgs, ... }:
49
50let
51 inherit (lib) mkIf mkOption types;
52 cfg = config.programs.man;
53in
54
55{
56 disabledModules = [ "services/programs/man.nix" ];
57
58 options = {
59 programs.man.enable = mkOption {
60 type = types.bool;
61 default = true;
62 description = "Whether to enable manual pages.";
63 };
64 };
65
66 config = mkIf cfg.enabled {
67 warnings = [ "disabled manpages for production deployments." ];
68 };
69}
70```