treewide: Mark Nix blocks in markdown as Nix

This should help us with highlighting and future formatting.

37 files changed, 106 insertions, 106 deletions

diff --git a/nixos/modules/i18n/input-method/default.md b/nixos/modules/i18n/input-method/default.md
index 42cb8a8d7b6a..3d56c97a1726 100644
--- a/nixos/modules/i18n/input-method/default.md
+++ b/nixos/modules/i18n/input-method/default.md
@@ -22,7 +22,7 @@ friendly input method user interface.
 
 The following snippet can be used to configure IBus:
 
-```
+```nix
 i18n.inputMethod = {
   enabled = "ibus";
   ibus.engines = with pkgs.ibus-engines; [ anthy hangul mozc ];
@@ -48,7 +48,7 @@ Available extra IBus engines are:
     methods, it must appear in the list of engines along with
     `table`. For example:
 
-    ```
+    ```nix
     ibus.engines = with pkgs.ibus-engines; [ table table-others ];
     ```
 
@@ -74,7 +74,7 @@ built-in Input Method Engine, Pinyin, QuWei and Table-based input methods.
 
 The following snippet can be used to configure Fcitx:
 
-```
+```nix
 i18n.inputMethod = {
   enabled = "fcitx5";
   fcitx5.addons = with pkgs; [ fcitx5-mozc fcitx5-hangul fcitx5-m17n ];
@@ -110,7 +110,7 @@ phonetic Korean characters (hangul) and pictographic Korean characters
 
 The following snippet can be used to configure Nabi:
 
-```
+```nix
 i18n.inputMethod = {
   enabled = "nabi";
 };
@@ -123,7 +123,7 @@ framework. Applications can use it through so-called bridges.
 
 The following snippet can be used to configure uim:
 
-```
+```nix
 i18n.inputMethod = {
   enabled = "uim";
 };
@@ -141,7 +141,7 @@ etc...
 
 The following snippet can be used to configure Hime:
 
-```
+```nix
 i18n.inputMethod = {
   enabled = "hime";
 };
@@ -153,7 +153,7 @@ Kime is Korean IME. it's built with Rust language and let you get simple, safe,
 
 The following snippet can be used to configure Kime:
 
-```
+```nix
 i18n.inputMethod = {
   enabled = "kime";
 };
diff --git a/nixos/modules/programs/digitalbitbox/default.md b/nixos/modules/programs/digitalbitbox/default.md
index 9bca14e97ffe..c93d0f2b7f0a 100644
--- a/nixos/modules/programs/digitalbitbox/default.md
+++ b/nixos/modules/programs/digitalbitbox/default.md
@@ -4,7 +4,7 @@ Digital Bitbox is a hardware wallet and second-factor authenticator.
 
 The `digitalbitbox` programs module may be installed by setting
 `programs.digitalbitbox` to `true` in a manner similar to
-```
+```nix
 programs.digitalbitbox.enable = true;
 ```
 and bundles the `digitalbitbox` package (see [](#sec-digitalbitbox-package)),
@@ -21,7 +21,7 @@ For more information, see <https://digitalbitbox.com/start_linux>.
 
 The binaries, `dbb-app` (a GUI tool) and `dbb-cli` (a CLI tool), are available
 through the `digitalbitbox` package which could be installed as follows:
-```
+```nix
 environment.systemPackages = [
   pkgs.digitalbitbox
 ];
@@ -31,13 +31,13 @@ environment.systemPackages = [
 
 The digitalbitbox hardware package enables the udev rules for Digital Bitbox
 devices and may be installed as follows:
-```
+```nix
 hardware.digitalbitbox.enable = true;
 ```
 
 In order to alter the udev rules, one may provide different values for the
 `udevRule51` and `udevRule52` attributes by means of overriding as follows:
-```
+```nix
 programs.digitalbitbox = {
   enable = true;
   package = pkgs.digitalbitbox.override {
diff --git a/nixos/modules/programs/plotinus.md b/nixos/modules/programs/plotinus.md
index fac3bbad1e08..b59d0d5c188b 100644
--- a/nixos/modules/programs/plotinus.md
+++ b/nixos/modules/programs/plotinus.md
@@ -12,6 +12,6 @@ palette provides a searchable list of of all menu items in the application.
 
 To enable Plotinus, add the following to your
 {file}`configuration.nix`:
-```
+```nix
 programs.plotinus.enable = true;
 ```
diff --git a/nixos/modules/programs/zsh/oh-my-zsh.md b/nixos/modules/programs/zsh/oh-my-zsh.md
index 6a310006edbf..7e4a41641eea 100644
--- a/nixos/modules/programs/zsh/oh-my-zsh.md
+++ b/nixos/modules/programs/zsh/oh-my-zsh.md
@@ -9,7 +9,7 @@ prompt themes.
 The module uses the `oh-my-zsh` package with all available
 features. The initial setup using Nix expressions is fairly similar to the
 configuration format of `oh-my-zsh`.
-```
+```nix
 {
   programs.zsh.ohMyZsh = {
     enable = true;
@@ -33,7 +33,7 @@ environment variable for this which points to a directory with additional
 scripts.
 
 The module can do this as well:
-```
+```nix
 {
   programs.zsh.ohMyZsh.custom = "~/path/to/custom/scripts";
 }
@@ -48,7 +48,7 @@ which bundles completion scripts and a plugin for `oh-my-zsh`.
 
 Rather than using a single mutable path for `ZSH_CUSTOM`,
 it's also possible to generate this path from a list of Nix packages:
-```
+```nix
 { pkgs, ... }:
 {
   programs.zsh.ohMyZsh.customPkgs = [
@@ -89,7 +89,7 @@ If third-party customizations (e.g. new themes) are supposed to be added to
     [upstream repo.](https://github.com/robbyrussell/oh-my-zsh/tree/91b771914bc7c43dd7c7a43b586c5de2c225ceb7/plugins)
 
 A derivation for `oh-my-zsh` may look like this:
-```
+```nix
 { stdenv, fetchFromGitHub }:
 
 stdenv.mkDerivation rec {
diff --git a/nixos/modules/services/backup/borgbackup.md b/nixos/modules/services/backup/borgbackup.md
index 39141f6ec858..64d9e35720f1 100644
--- a/nixos/modules/services/backup/borgbackup.md
+++ b/nixos/modules/services/backup/borgbackup.md
@@ -21,7 +21,7 @@ A complete list of options for the Borgbase module may be found
 ## Basic usage for a local backup {#opt-services-backup-borgbackup-local-directory}
 
 A very basic configuration for backing up to a locally accessible directory is:
-```
+```nix
 {
     opt.services.borgbackup.jobs = {
       { rootBackup = {
@@ -59,7 +59,7 @@ ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAID78zmOyA+5uPG4Ot0hfAy+sLDPU1L4AiIoRYEIVbbQ/
 ```
 
 Add the following snippet to your NixOS configuration:
-```
+```nix
 {
   services.borgbackup.repos = {
     my_borg_repo = {
@@ -80,7 +80,7 @@ that you have stored a secret passphrasse in the file
 {file}`/run/keys/borgbackup_passphrase`, which should be only
 accessible by root
 
-```
+```nix
 {
   services.borgbackup.jobs = {
     backupToLocalServer = {
diff --git a/nixos/modules/services/databases/foundationdb.md b/nixos/modules/services/databases/foundationdb.md
index 0815c139152f..af17c9f95999 100644
--- a/nixos/modules/services/databases/foundationdb.md
+++ b/nixos/modules/services/databases/foundationdb.md
@@ -15,7 +15,7 @@ key-value store.
 
 To enable FoundationDB, add the following to your
 {file}`configuration.nix`:
-```
+```nix
 services.foundationdb.enable = true;
 services.foundationdb.package = pkgs.foundationdb71; # FoundationDB 7.1.x
 ```
@@ -109,7 +109,7 @@ default configuration. See below for more on scaling to increase this.
 FoundationDB stores all data for all server processes under
 {file}`/var/lib/foundationdb`. You can override this using
 {option}`services.foundationdb.dataDir`, e.g.
-```
+```nix
 services.foundationdb.dataDir = "/data/fdb";
 ```
 
@@ -265,7 +265,7 @@ directories.
 For example, to create backups in {command}`/opt/fdb-backups`, first
 set up the paths in the module options:
 
-```
+```nix
 services.foundationdb.extraReadWritePaths = [ "/opt/fdb-backups" ];
 ```
 
diff --git a/nixos/modules/services/databases/postgresql.md b/nixos/modules/services/databases/postgresql.md
index 3ff1f00fa9cf..ce1f2856b019 100644
--- a/nixos/modules/services/databases/postgresql.md
+++ b/nixos/modules/services/databases/postgresql.md
@@ -15,7 +15,7 @@ PostgreSQL is an advanced, free relational database.
 ## Configuring {#module-services-postgres-configuring}
 
 To enable PostgreSQL, add the following to your {file}`configuration.nix`:
-```
+```nix
 services.postgresql.enable = true;
 services.postgresql.package = pkgs.postgresql_15;
 ```
@@ -35,7 +35,7 @@ alice=>
 -->
 
 By default, PostgreSQL stores its databases in {file}`/var/lib/postgresql/$psqlSchema`. You can override this using [](#opt-services.postgresql.dataDir), e.g.
-```
+```nix
 services.postgresql.dataDir = "/data/postgresql";
 ```
 
@@ -174,7 +174,7 @@ $ nix-instantiate --eval -A postgresql_13.psqlSchema
 "13"
 ```
 For an upgrade, a script like this can be used to simplify the process:
-```
+```nix
 { config, pkgs, ... }:
 {
   environment.systemPackages = [
@@ -256,7 +256,7 @@ postgresql_15.pkgs.pg_partman        postgresql_15.pkgs.pgroonga
 ```
 
 To add plugins via NixOS configuration, set `services.postgresql.extraPlugins`:
-```
+```nix
 services.postgresql.package = pkgs.postgresql_12;
 services.postgresql.extraPlugins = ps: with ps; [
   pg_repack
@@ -265,7 +265,7 @@ services.postgresql.extraPlugins = ps: with ps; [
 ```
 
 You can build custom PostgreSQL-with-plugins (to be used outside of NixOS) using function `.withPackages`. For example, creating a custom PostgreSQL package in an overlay can look like:
-```
+```nix
 self: super: {
   postgresql_custom = self.postgresql_12.withPackages (ps: [
     ps.pg_repack
@@ -275,7 +275,7 @@ self: super: {
 ```
 
 Here's a recipe on how to override a particular plugin through an overlay:
-```
+```nix
 self: super: {
   postgresql_15 = super.postgresql_15// {
     pkgs = super.postgresql_15.pkgs // {
diff --git a/nixos/modules/services/databases/tigerbeetle.md b/nixos/modules/services/databases/tigerbeetle.md
index 47394d443059..ed05c982350d 100644
--- a/nixos/modules/services/databases/tigerbeetle.md
+++ b/nixos/modules/services/databases/tigerbeetle.md
@@ -7,7 +7,7 @@
 TigerBeetle is a distributed financial accounting database designed for mission critical safety and performance.
 
 To enable TigerBeetle, add the following to your {file}`configuration.nix`:
-```
+```nix
   services.tigerbeetle.enable = true;
 ```
 
@@ -20,7 +20,7 @@ By default, TigerBeetle will only listen on a local interface.
 To configure it to listen on a different interface (and to configure it to connect to other replicas, if you're creating more than one), you'll have to set the `addresses` option.
 Note that the TigerBeetle module won't open any firewall ports automatically, so if you configure it to listen on an external interface, you'll need to ensure that connections can reach it:
 
-```
+```nix
   services.tigerbeetle = {
     enable = true;
     addresses = [ "0.0.0.0:3001" ];
diff --git a/nixos/modules/services/desktops/flatpak.md b/nixos/modules/services/desktops/flatpak.md
index af71d85b5a15..57aa41b56224 100644
--- a/nixos/modules/services/desktops/flatpak.md
+++ b/nixos/modules/services/desktops/flatpak.md
@@ -8,7 +8,7 @@ Flatpak is a system for building, distributing, and running sandboxed desktop
 applications on Linux.
 
 To enable Flatpak, add the following to your {file}`configuration.nix`:
-```
+```nix
   services.flatpak.enable = true;
 ```
 
@@ -16,7 +16,7 @@ For the sandboxed apps to work correctly, desktop integration portals need to
 be installed. If you run GNOME, this will be handled automatically for you;
 in other cases, you will need to add something like the following to your
 {file}`configuration.nix`:
-```
+```nix
   xdg.portal.extraPortals = [ pkgs.xdg-desktop-portal-gtk ];
   xdg.portal.config.common.default = "gtk";
 ```
diff --git a/nixos/modules/services/development/athens.md b/nixos/modules/services/development/athens.md
index 77663db509d5..142cc74b5d0d 100644
--- a/nixos/modules/services/development/athens.md
+++ b/nixos/modules/services/development/athens.md
@@ -18,7 +18,7 @@ A complete list of options for the Athens module may be found
 ## Basic usage for a caching proxy configuration {#opt-services-development-athens-caching-proxy}
 
 A very basic configuration for Athens that acts as a caching and forwarding HTTP proxy is:
-```
+```nix
 {
     services.athens = {
       enable = true;
@@ -28,7 +28,7 @@ A very basic configuration for Athens that acts as a caching and forwarding HTTP
 
 If you want to prevent Athens from writing to disk, you can instead configure it to cache modules only in memory:
 
-```
+```nix
 {
     services.athens = {
       enable = true;
@@ -39,7 +39,7 @@ If you want to prevent Athens from writing to disk, you can instead configure it
 
 To use the local proxy in Go builds, you can set the proxy as environment variable:
 
-```
+```nix
 {
   environment.variables = {
     GOPROXY = "http://localhost:3000"
diff --git a/nixos/modules/services/development/blackfire.md b/nixos/modules/services/development/blackfire.md
index e2e7e4780c79..5a7fbe68f7d2 100644
--- a/nixos/modules/services/development/blackfire.md
+++ b/nixos/modules/services/development/blackfire.md
@@ -7,7 +7,7 @@
 [Blackfire](https://blackfire.io) is a proprietary tool for profiling applications. There are several languages supported by the product but currently only PHP support is packaged in Nixpkgs. The back-end consists of a module that is loaded into the language runtime (called *probe*) and a service (*agent*) that the probe connects to and that sends the profiles to the server.
 
 To use it, you will need to enable the agent and the probe on your server. The exact method will depend on the way you use PHP but here is an example of NixOS configuration for PHP-FPM:
-```
+```nix
 let
   php = pkgs.php.withExtensions ({ enabled, all }: enabled ++ (with all; [
     blackfire
diff --git a/nixos/modules/services/development/livebook.md b/nixos/modules/services/development/livebook.md
index 5315f2c2755a..3a3d9584675b 100644
--- a/nixos/modules/services/development/livebook.md
+++ b/nixos/modules/services/development/livebook.md
@@ -9,7 +9,7 @@ Enabling the `livebook` service creates a user
 [`systemd`](https://www.freedesktop.org/wiki/Software/systemd/) unit
 which runs the server.
 
-```
+```nix
 { ... }:
 
 {
@@ -51,6 +51,6 @@ some features require additional packages.  For example, the machine
 learning Kinos require `gcc` and `gnumake`.  To add these, use
 `extraPackages`:
 
-```
+```nix
 services.livebook.extraPackages = with pkgs; [ gcc gnumake ];
 ```
diff --git a/nixos/modules/services/editors/emacs.md b/nixos/modules/services/editors/emacs.md
index 02f47b098d86..9164ee2adcb5 100644
--- a/nixos/modules/services/editors/emacs.md
+++ b/nixos/modules/services/editors/emacs.md
@@ -178,7 +178,7 @@ file {file}`configuration.nix` to make it contain:
 ::: {.example #module-services-emacs-configuration-nix}
 ### Custom Emacs in `configuration.nix`
 
-```
+```nix
 {
  environment.systemPackages = [
    # [...]
@@ -203,7 +203,7 @@ adding it to your {file}`~/.config/nixpkgs/config.nix` (see
 ::: {.example #module-services-emacs-config-nix}
 ### Custom Emacs in `~/.config/nixpkgs/config.nix`
 
-```
+```nix
 {
   packageOverrides = super: let self = super.pkgs; in {
     myemacs = import ./emacs.nix { pkgs = self; };
@@ -228,7 +228,7 @@ only use {command}`emacsclient`), you can change your file
 ::: {.example #ex-emacsGtk3Nix}
 ### Custom Emacs build
 
-```
+```nix
 { pkgs ? import <nixpkgs> {} }:
 let
   myEmacs = (pkgs.emacs.override {
@@ -262,7 +262,7 @@ with the user's login session.
 
 To install and enable the {command}`systemd` user service for Emacs
 daemon, add the following to your {file}`configuration.nix`:
-```
+```nix
 services.emacs.enable = true;
 ```
 
@@ -323,7 +323,7 @@ In general, {command}`systemd` user services are globally enabled
 by symlinks in {file}`/etc/systemd/user`. In the case where
 Emacs daemon is not wanted for all users, it is possible to install the
 service but not globally enable it:
-```
+```nix
 services.emacs.enable = false;
 services.emacs.install = true;
 ```
diff --git a/nixos/modules/services/mail/mailman.md b/nixos/modules/services/mail/mailman.md
index 55b61f8a2582..446aa1f921b6 100644
--- a/nixos/modules/services/mail/mailman.md
+++ b/nixos/modules/services/mail/mailman.md
@@ -9,7 +9,7 @@ an existing, securely configured Postfix setup, as it does not automatically con
 ## Basic usage with Postfix {#module-services-mailman-basic-usage}
 
 For a basic configuration with Postfix as the MTA, the following settings are suggested:
-```
+```nix
 { config, ... }: {
   services.postfix = {
     enable = true;
@@ -50,7 +50,7 @@ necessary, but outside the scope of the Mailman module.
 ## Using with other MTAs {#module-services-mailman-other-mtas}
 
 Mailman also supports other MTA, though with a little bit more configuration. For example, to use Mailman with Exim, you can use the following settings:
-```
+```nix
 { config, ... }: {
   services = {
     mailman = {
diff --git a/nixos/modules/services/matrix/mjolnir.md b/nixos/modules/services/matrix/mjolnir.md
index f6994eeb8fa5..2594f05ce27b 100644
--- a/nixos/modules/services/matrix/mjolnir.md
+++ b/nixos/modules/services/matrix/mjolnir.md
@@ -46,7 +46,7 @@ autoconfigure a new Pantalaimon instance, which will connect to the homeserver
 set in [services.mjolnir.homeserverUrl](#opt-services.mjolnir.homeserverUrl) and Mjolnir itself
 will be configured to connect to the new Pantalaimon instance.
 
-```
+```nix
 {
   services.mjolnir = {
     enable = true;
@@ -78,7 +78,7 @@ uses across an entire homeserver.
 To use the Antispam Module, add `matrix-synapse-plugins.matrix-synapse-mjolnir-antispam`
 to the Synapse plugin list and enable the `mjolnir.Module` module.
 
-```
+```nix
 {
   services.matrix-synapse = {
     plugins = with pkgs; [
diff --git a/nixos/modules/services/matrix/synapse.md b/nixos/modules/services/matrix/synapse.md
index 9c9c025fc5f5..7f6587ce09df 100644
--- a/nixos/modules/services/matrix/synapse.md
+++ b/nixos/modules/services/matrix/synapse.md
@@ -23,7 +23,7 @@ synapse server for the `example.org` domain, served from
 the host `myhostname.example.org`. For more information,
 please refer to the
 [installation instructions of Synapse](https://element-hq.github.io/synapse/latest/setup/installation.html) .
-```
+```nix
 { pkgs, lib, config, ... }:
 let
   fqdn = "${config.networking.hostName}.${config.networking.domain}";
@@ -158,7 +158,7 @@ in an additional file like this:
     by `matrix-synapse`.
   - Include the file like this in your configuration:
 
-    ```
+    ```nix
     {
       services.matrix-synapse.extraConfigFiles = [
         "/run/secrets/matrix-shared-secret"
@@ -190,7 +190,7 @@ fill in the required connection details automatically when you enter your
 Matrix Identifier. See
 [Try Matrix Now!](https://matrix.org/docs/projects/try-matrix-now.html)
 for a list of existing clients and their supported featureset.
-```
+```nix
 {
   services.nginx.virtualHosts."element.${fqdn}" = {
     enableACME = true;
diff --git a/nixos/modules/services/misc/anki-sync-server.md b/nixos/modules/services/misc/anki-sync-server.md
index 5d2b4da4d2fc..f58d3d8ad0da 100644
--- a/nixos/modules/services/misc/anki-sync-server.md
+++ b/nixos/modules/services/misc/anki-sync-server.md
@@ -16,7 +16,7 @@ unit which runs the sync server with an isolated user using the systemd
 `DynamicUser` option.
 
 This can be done by enabling the `anki-sync-server` service:
-```
+```nix
 { ... }:
 
 {
@@ -27,7 +27,7 @@ This can be done by enabling the `anki-sync-server` service:
 It is necessary to set at least one username-password pair under
 {option}`services.anki-sync-server.users`. For example
 
-```
+```nix
 {
   services.anki-sync-server.users = [
     {
@@ -50,7 +50,7 @@ you want to expose the sync server directly to other computers (not recommended
 in most circumstances, because the sync server doesn't use HTTPS), then set the
 following options:
 
-```
+```nix
 {
   services.anki-sync-server.host = "0.0.0.0";
   services.anki-sync-server.openFirewall = true;
diff --git a/nixos/modules/services/misc/gitlab.md b/nixos/modules/services/misc/gitlab.md
index 916b23584ed0..ea1b95607c63 100644
--- a/nixos/modules/services/misc/gitlab.md
+++ b/nixos/modules/services/misc/gitlab.md
@@ -10,7 +10,7 @@ configure a webserver to proxy HTTP requests to the socket.
 
 For instance, the following configuration could be used to use nginx as
 frontend proxy:
-```
+```nix
 services.nginx = {
   enable = true;
   recommendedGzipSettings = true;
@@ -35,7 +35,7 @@ The default state dir is `/var/gitlab/state`. This is where
 all data like the repositories and uploads will be stored.
 
 A basic configuration with some custom settings could look like this:
-```
+```nix
 services.gitlab = {
   enable = true;
   databasePasswordFile = "/var/keys/gitlab/db_password";
diff --git a/nixos/modules/services/misc/sourcehut/default.md b/nixos/modules/services/misc/sourcehut/default.md
index 44d58aa0bef3..5f841833a954 100644
--- a/nixos/modules/services/misc/sourcehut/default.md
+++ b/nixos/modules/services/misc/sourcehut/default.md
@@ -12,7 +12,7 @@ This NixOS module also provides basic configuration integrating Sourcehut into l
 and `services.postgresql` services.
 
 A very basic configuration may look like this:
-```
+```nix
 { pkgs, ... }:
 let
   fqdn =
diff --git a/nixos/modules/services/misc/weechat.md b/nixos/modules/services/misc/weechat.md
index 21f41be5b4a0..fb20ebe1e4db 100644
--- a/nixos/modules/services/misc/weechat.md
+++ b/nixos/modules/services/misc/weechat.md
@@ -12,7 +12,7 @@ unit which runs the chat client in a detached
 session.
 
 This can be done by enabling the `weechat` service:
-```
+```nix
 { ... }:
 
 {
@@ -30,7 +30,7 @@ allow your another user to attach to this session, the
 `screenrc` needs to be tweaked by adding
 [multiuser](https://www.gnu.org/software/screen/manual/html_node/Multiuser.html#Multiuser)
 support:
-```
+```nix
 {
   programs.screen.screenrc = ''
     multiuser on
diff --git a/nixos/modules/services/monitoring/goss.md b/nixos/modules/services/monitoring/goss.md
index 1e636aa3bdf3..bf91d42011fa 100644
--- a/nixos/modules/services/monitoring/goss.md
+++ b/nixos/modules/services/monitoring/goss.md
@@ -7,7 +7,7 @@ for validating a server's configuration.
 
 A minimal configuration looks like this:
 
-```
+```nix
 {
   services.goss = {
     enable = true;
diff --git a/nixos/modules/services/monitoring/prometheus/exporters.md b/nixos/modules/services/monitoring/prometheus/exporters.md
index 34fadecadc74..84de17789601 100644
--- a/nixos/modules/services/monitoring/prometheus/exporters.md
+++ b/nixos/modules/services/monitoring/prometheus/exporters.md
@@ -9,7 +9,7 @@ One of the most common exporters is the
 [node exporter](https://github.com/prometheus/node_exporter),
 it provides hardware and OS metrics from the host it's
 running on. The exporter could be configured as follows:
-```
+```nix
   services.prometheus.exporters.node = {
     enable = true;
     port = 9100;
@@ -35,7 +35,7 @@ configuration see `man configuration.nix` or search through
 the [available options](https://nixos.org/nixos/options.html#prometheus.exporters).