nixos-option: add page (#7166)

pages/linux/nixos-option.md

@@ -0,0 +1,28 @@
+# nixos-option
+
+> Inspect a NixOS configuration.
+> More information: <https://nixos.org/manual/nixos/stable/index.html#sec-modularity>.
+
+- List all subkeys of a given option key:
+
+`nixos-option {{option_key}}`
+
+- List current boot kernel modules:
+
+`nixos-option boot.kernelModules`
+
+- List authorized keys for a specific user:
+
+`nixos-option users.users.{{username}}.openssh.authorizedKeys.{{keyFiles|keys}}`
+
+- List all remote builders:
+
+`nixos-option nix.buildMachines`
+
+- List all subkeys of a given key on another NixOS configuration:
+
+`NIXOS_CONFIG={{path_to_configuration.nix}} nixos-option {{option_key}}`
+
+- Show recursively all values of a user:
+
+`nixos-option -r users.users.{{user}}`