Use impermanence

README.org

@@ -15,6 +15,8 @@
 
     nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
 
+    impermanence.url = "github:nix-community/impermanence";
+
     home-manager = {
       url = "github:nix-community/home-manager";
       inputs.nixpkgs.follows = "nixpkgs";
@@ -70,6 +72,7 @@ let mkHost = k: v: nixpkgs.lib.nixosSystem {
         inputs.self.nixosModules.default
 
         inputs.disko.nixosModules.disko
+        inputs.impermanence.nixosModules.impermanence
 
         # Directory name should always match host name.
         ({ ... }: { networking.hostName = k; })
@@ -102,6 +105,15 @@ builtins.mapAttrs mkHost (builtins.readDir ./hosts)
   ];
 
   sydnix = {
+    impermanence = {
+      enable = true;
+      directories = [
+        # Warning: Neither /var/lib/nixos nor any of its parents are persisted.
+        # This means all users/groups without specified uids/gids will have them
+        # reassigned on reboot.
+        "/var/lib/nixos"
+      ];
+    };
     users.users = [
       "crumb"
     ];